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<?xml version="1.0" encoding="UTF-8"?>
<archimedes>
  <info>
    <author>Volta, Alessandro</author>
    <title>Nuova Memoria sull'Elettricita Animale - Lettera Terza</title>
    <date>1795</date>
    <place>Como</place>
    <translator/>
    <lang>it</lang>
    <cvs_file>volta_nuoMemLetTerz_922_it_1795.xml</cvs_file>
    <cvs_version/>
    <locator>922.xml</locator>
  	<echodir>/permanent/volta_collected_papers/volta_nuoMemLetTerz_922_it_1795</echodir>
  </info>
  <text>
    <front>
      <section>
        <pb/>
        <p id="N10018" type="head">
          <s id="N1001A">
					LETTERA TERZA
					<lb/>
					DEL SIG. CAV.
					<lb/>
					DON ALESSANDRO VOLTA
					<lb/>
					P. PROFESSORE, EC.
					<lb/>
					AL SIG. AB.
					<lb/>
					ANTON MARIA VASSALLI
					<lb/>
					PROFESSORE DI FISICA A TORINO, EC.
					<lb/>
					SULL’ELETTRICITÀ ANIMALE.
				</s>
        </p>
        <p id="N1002A" type="main">
          <s id="N1002C">
					<emph type="italics"/>Como, 27 Ottobre 1795. <emph.end type="italics"/>
				</s>
        </p>
      </section>
      <section type="editorcomment">
        <p id="N10036" type="head">
          <s id="N10038">
					FONTI.
				</s>
        </p>
        <p id="N1003A" type="main">
          <s id="N1003C">
					STAMPATE.
					<lb/>
					Br. Ann. T. XI. 1796. pg. 84.
					<lb/>
					Ant. Coll. T. II. P. I. pg. 230.
				</s>
        </p>
        <p id="N10042" type="main">
          <s id="N10044">
					MANOSCRITTE.
					<lb/>
					Copia presso Ac. Sc. Torino. (B. XI.8).
					<lb/>
					Cart. Volt.: J 27; J 32; J 49; L 14;
					<lb/>
					L 15.
				</s>
        </p>
        <p id="N1004C" type="main">
          <s id="N1004E">
					OSSERVAZIONI.
					<lb/>
					TITOLO: Da Br. Ann.
					<lb/>
					DATA: dalla copia presso Acc. Sc. Tor.
					<lb/>
					in Br. Ann. trovasi 24 ottobre 1795.
				</s>
        </p>
        <p id="N10056" type="main">
          <s id="N10058">
					J 27 contiene un abbozzo della Scala dei poteri elettromotori analoga a quella con-<lb/>
          			tenuta in questo numero.
				</s>
          <lb/>
          <s id="N1005D">
					J 32. Prime minute più ristrette da cui togliesi una nota.
				</s>
          <lb/>
          <s id="N10060">
					L. 14. Vari fogli che nel loro assieme formano quasi tutta la lettera.
				</s>
          <lb/>
          <s id="N10063">
					L. 15. Vari fogli che contengono le note.
				</s>
          <lb/>
          <s id="N10066">
					Un brano di questa lettera leggesi nel « Manuale della letteratura italiana » compi-<lb/>
					lato dai professori A. D’Ancona ed O. Bacci (Firenze, 1897, Barbera), Vol. IV, pag. 562.
				</s>
        </p>
        <pb/>
        <p id="N1006B" type="main">
          <s id="N1006D">
					[Empty Page]
				</s>
        </p>
      </section>
      <section>
        <pb/>
        <p id="N10071" type="head">
          <s id="N10073">
					LETTERA TERZA.
				</s>
        </p>
      </section>
    </front>
    <body>
      <chap>
        <p id="N10077" type="main">
          <s id="N10079">
					<emph type="italics"/>da Como li 27 8bre 1795. <emph.end type="italics"/>
				</s>
        </p>
        <p id="N10081" type="main">
          <s id="N10083">
					Dopo le due lunghe lettere da me scrittevi, illustre Accademico e Collega,
					<lb/>
					ha già un anno e mezzo, e inserite ne’ Giornali del nostro comune amico Dr. BRU-<lb/>
					GNATELLI, sul soggetto della pretesa <emph type="italics"/>Elettricità animale<emph.end type="italics"/>, propria cioè degli or-<lb/>
					gani, in cui si suppone una carica o sbilancio qualsiasi di fluido elettrico, quale
					<lb/>
					elettricità organica ideata dal valente Fisico e Professore di Anatomia Dr. GAL-<lb/>
					VANI dietro le bellissime sue sperienze e scoperte invero mirabili ammisi io
					<lb/>
					pure per qualche tempo, ma presto cominciai a rivocare in dubbio, e finalmente .
					<lb/>
					dovetti con dispiacere riconoscere e dichiarare per insussistente [l]: dopo che
					<lb/>
					dalla maggior parte de’ Fisici, massime oltramontani, erasi adottata la mia opi-<lb/>
					nione, esposta nelle mentovate lettere e in altre memorie e scritti antecedenti,
					<lb/>
					che riconosce bensì nelle sperienze di cui si tratta, una vera elettricità [2],
					<lb/>
					ma elettricità meramente artificiale ed estrinseca, mossa cioè da conduttori
					<lb/>
					acconciamente applicati; risvegliossi di nuovo qui in Italia, e crebbe più che
					<lb/>
					mai il fermento delle contrarie opinioni in occasione che si pubblicarono
					<lb/>
					nell’autunno scorso con un opuscolo del Dr. EUSEBIO VALLI delle nuove interes-<lb/>
					santi sperienze in soccorso del primo ormai abbandonato sistema.
				</s>
          <s id="N100A9">
					Invero tali
					<lb/>
					sperienze non solo comparvero favorevoli e consentanee all’ipotesi di un’elet-<lb/>
					tricità propria e attiva degli organi animali, di una vera carica o sbilancio
					<lb/>
					di fluido elettrico tra nervi e muscoli dipendenti, o tra l’interno e l’esterno
					<lb/>
					di essi muscoli, la qual carica o sbilancio producasi naturalmente per le forze
					<lb/>
					della vita, e manifestisi anche negli animali trucidati, e ne’ membri recisi,
					<lb/>
					finchè vi dura un certo grado di vitalità; non solo, dico, parvero tali sperienze
					<lb/>
					favorire grandemente siffatta ipotesi, altronde bella e seducente, proposta dal
					<lb/>
					prefato illustre Professor Bolognese adottata e difesa contro le forti mie obbie-<lb/>
					zioni da ALDINI suo nipote e collega, e da altri seguaci non pochi; ma sembra-<lb/>
					rono dimostrarla evidentemente, e porla fuori d’ogni dubbio; e sì ne imposero
					<lb/>
					a molti, e tiraronli di nuovo agli stendardi Galvaniani quando già soscritto
					<lb/>
					aveano, o stavano per soscrivere alla mia sentenza affatto diversa.
				</s>
        </p>
        <p id="N100C3" type="main">
          <s id="N100C5">
					Questa, che sostenni già con molti argomenti e prove sperimentali, e che
					<lb/>
					<pb pagenum="290"/>
					sostengo ancora, riduce tutto ad un giuoco de’ conduttori in conveniente
					<lb/>
					modo applicati, alla virtù cioè che loro attribuisco, o dirò meglio di cui ho sco-<lb/>
					perto esser essi dotati, d’impellere e smuovere, ove si affrontino o combacino
					<lb/>
					alcuni di classe o di specie diversa, il fluido elettrico: dal che poi viene che se
					<lb/>
					concorrano tre, o più, tutti diversi a compiere il circolo conduttore, se p. e.
					<lb/>
					a due metalli, argento e ferro, piombo ed ottone, argento e zinco ecc. sia in-<lb/>
					terposto uno o più conduttori non metallici, della classe cioè da me chiamata
					<lb/>
					de’ <emph type="italics"/>conduttori umidi<emph.end type="italics"/>, perchè o fluidi in tutta la massa, o contenenti qualche
					<lb/>
					umore, fra i quali i corpi animali e tutte le loro parti fresche e succose; se, dico,
					<lb/>
					un conduttore di questa 2<emph type="sup"/>a<emph.end type="sup"/> classe trovisi di mezzo e a contatto di due di
					<lb/>
					quella 1<emph type="sup"/>a<emph.end type="sup"/>, di due metalli diversi, ne viene che si determini una corrente continua
					<lb/>
					di fluido elettrico, secondo che l’azione su di esso in virtù di tali combaciamenti
					<lb/>
					prevale da una parte o dall’altra
					<note n="a">
					<p id="N100F9" type="main">
						<s id="N100FC">
							Ciò basta per mostrare quanto sia diversa dalla pretesa elettricità animale, dalle
							<lb/>
							idee di GALVANI e suoi seguaci, quell’elettricità che sostengo io; la quale non suppone alcuna
							<lb/>
							carica o sbilancio, e conseguente scarica degli organi animali, e neppure carica o scarica pro-<lb/>
							priamente detta de’ conduttori applicati, ma una circolazione, ossia corrente continua di
							<lb/>
							fluido elettrico, cagionata e mantenuta da una forza arcana, che risulta dal combaciamento
							<lb/>
							di conduttori diversi fra loro; i quali in simili circostanze sono qualche cosa più che semplici
							<lb/>
							deferenti, facendola da veri <emph type="italics"/>eccitatori<emph.end type="italics"/> o <emph type="italics"/>motori<emph.end type="italics"/>.
						</s>
					</p>
				</note>
				.
			</s>
        </p>
        <p id="N10119" type="main">
          <s id="N1011B">
				Tale mia spiegazione venendo confermata da innumerabili sperienze va-<lb/>
				riate in molte maniere, come ho fatto vedere in diversi scritti, e bastando solo
				<lb/>
				a render ragione di tanti fenomeni e apparenti anomalie in ogni altra guisa
				<lb/>
				inesplicabili, ho dovuto indurne che la pretesa elettricità animale, propria e
				<lb/>
				attiva degli organi, non ha fondamento, molto meno prove decisive che la
				<lb/>
				dimostrino: che conseguentemente gli organi animali in simili sperienze vo-<lb/>
				gliono risguardarsi come puramente <emph type="italics"/>passivi<emph.end type="italics"/>, come semplici <emph type="italics"/>elettroscopj<emph.end type="italics"/> di un
				<lb/>
				genere particolare; e che debbono invece aversi per <emph type="italics"/>attivi<emph.end type="italics"/> i Conduttori appli-<lb/>
				cati al mutuo combaciamento, purchè diversi; e tanto appunto più attivi ed
				<lb/>
				efficaci quanto più differiscono tra loro sotto certi rapporti.
			</s>
        </p>
        <p id="N10141" type="main">
          <s id="N10143">
				Così ho conchiuso sono già tre anni circa [3], e così sostengo ancora, torno
				<lb/>
				a ripetere, a fronte delle nuove mentovate sperienze del Dr. VALLI, ed altre
				<lb/>
				di simil fatta; le quali con tutta l’apparenza favorevole alla teoria di GALVANI,
				<lb/>
				per cui furono avidamente abbracciate da’ suoi partigiani, che ne menarono
				<lb/>
				gran rumore; vedremo che esaminate in tutte le loro circostanze e aggiunti,
				<lb/>
				moltiplicate e variate come si conviene, comprovano anzi evidentemente l’opi-<lb/>
				nione mia, e non lasciano a quell’altra più alcun appiglio o risorsa.
			</s>
        </p>
        <p id="N10151" type="main">
          <s id="N10153">
				Io non so se tra quelli che stanno ancora per l’elettricità animale vera e
				<lb/>
				propria nel senso sopra spiegato, vi troviate ancor voi, mio caro professore,
				<lb/>
				a cui è piaciuto sempre di ampliare, forse anche troppo, l’impero dell’elettri-<lb/>
				<pb pagenum="291"/>
				cismo, e sottomettere alla sua influenza il più gran numero possibile di feno-<lb/>
				meni naturali, e in particolare alcuni dell’economia vegetabile ed animale,
				<lb/>
				e che anzi prevenuto vi mostraste in alcune operette dalle idee di un’elettri-<lb/>
				cità spontanea negli animali, e molto vi studiaste di comprovarla con esperienze
				<lb/>
				varie, alcune delle quali veramente curiose, e ciò molto innanzi che fosser note
				<lb/>
				quelle affatto sorprendenti di GALVANI: non so bene qual impressione vi abbian
				<lb/>
				fatta dapprima tali sperienze del Prof.<emph type="sup"/>re<emph.end type="sup"/> Bolognese; in seguito le mie molto
				<lb/>
				più estese e variate, dalle quali ho tratto conseguenze ben diverse e in nulla
				<lb/>
				favorevoli alla supposta elettricità animale, e finalmente le nuove di VALLI
				<lb/>
				ed altre analoghe, con cui si è preteso di ristabilirla inconcussamente.
			</s>
          <s id="N10176">
				So che
				<lb/>
				queste ultime ne hanno imposto a molti, come già dissi; i quali veggendo
				<lb/>
				ottenersi in qualche modo le convulsioni nelle rane di fresco preparate e sensi-<lb/>
				bilissime, anche senza l’intervento di alcun conduttore metallico o carbone,
				<lb/>
				ciò ch’io avea pronunciato non succedere mai [4], perchè non m’era fino allora
				<lb/>
				riuscito (e infatti non riesce che difficilmente) non cercarono dippiù per darla
				<lb/>
				vinta ai sostenitori dell’elettricita animale in senso proprio, della pretesa ca-<lb/>
				rica cioè o sbilancio di fluido elettrico tra nervi e rispettivi muscoli, o tra l’in-<lb/>
				terno e l’esterno di essi muscoli.
			</s>
          <s id="N10188">
				Eppure in niun modo vien provata da tali
				<lb/>
				sperienze siffatta elettricità animale, come mi propongo di far vedere: esse
				<lb/>
				mostrano soltanto, che sono io andato troppo innanzi asserendo, che non si
				<lb/>
				potrebbe mai coll’applicazione di soli conduttori umidi, ossia di 2<emph type="sup"/>a<emph.end type="sup"/> classe,
				<lb/>
				senza l’intervento cioè di alcun metallo o conduttore di 1<emph type="sup"/>a<emph.end type="sup"/> classe, eccitare le
				<lb/>
				convulsioni nelle rane comunque preparate e facilissime a risentirsi.
			</s>
          <s id="N101A0">
				Ecco in
				<lb/>
				che debbo ritrattarmi, ossia correggere le espressioni troppo generali da me
				<lb/>
				avanzate: non già riguardo alla proposizione capitale, che ho sostenuta, e
				<lb/>
				che sostengo ancora, cioè che la mossa al fluido elettrico vien data, non già
				<lb/>
				dagli organi animali in cui trovisi esso fluido, come suppongono i Galvaniani,
				<lb/>
				in uno stato di carica o di sbilancio; bensì da una forza che risulta dal comba-<lb/>
				ciamento di conduttori dissimili che entrano nel circolo: che insomma ella è
				<lb/>
				anche in tali sperienze, in cui non s’adoprano metalli, un’elettricità artificiale
				<lb/>
				eccitata da causa estrinseca, ossia movente esterno, e in niun modo da prin-<lb/>
				cipio o forza interna degli organi animali, de’ nervi e muscoli.
			</s>
        </p>
        <p id="N101B4" type="main">
          <s id="N101B6">
				Per venire ora più davvicino a codeste sperienze, non mi fa stupore che
				<lb/>
				abbian sorpreso e tirato molti, che prima ne dubitavano, a credere alla supposta
				<lb/>
				elettricità animale, e a dichiararsi apertamente per essa; tutti quelli cioè, che
				<lb/>
				non sono andati più innanzi, e non han fatto il dovuto riflesso alle circostanze.
			</s>
          <lb/>
          <s id="N101BF">
				Senza questo dovettero restare sedotti (e chi poteva non esserlo a prima
				<lb/>
				giunta?) dal vedere eccitarsi delle contrazioni più o meno forti in tutti i mu-<lb/>
				scoli delle gambe posteriori di una rana compitamente preparata, con ripie-<lb/>
				gare semplicemente una di esse gambe, e addurla al contatto de’ nervi ischia-<lb/>
				tici ossia crurali, oppur de’ muscoli del dorso.
			</s>
        </p>
        <pb pagenum="292"/>
        <p id="N101CB" type="main">
          <s id="N101CD">
				Codesta è l’esperienza principale, con cui crede VALLI, e credono i Galva-<lb/>
				niani tutti vecchj e nuovi, di aver vinta la causa contro di me, e fino di avermi
				<lb/>
				ridotto al silenzio.
			</s>
          <s id="N101D3">
				Altre sperienze consimili son quelle di tenere sospesa pe’
				<lb/>
				piedi la rana con una mano, e con un dito dell’altra o colla lingua toccare i
				<lb/>
				nervi crurali pendenti, o la porzione di spina, che ad essi si è lasciata attaccata;
				<lb/>
				di tener in egual modo sospesa la rana per una gamba, far passare detta spina,
				<lb/>
				o buona parte del tronco, se tutto o quasi tutto è rimasto attaccato [5] (come
				<lb/>
				io pratico perloppiù di lasciarvelo, troncandone la sola testa), nell’acqua di
				<lb/>
				un catino, e portare l’altra sua gamba al contatto dell’acqua medesima; nel-<lb/>
				l’uno e nell’altro de’ quali modi succede pure qualche volta di eccitare le con-<lb/>
				vulsioni; come succede in quell’altra maniera descritta già nell’operetta ano-<lb/>
				nima (intitolata <emph type="italics"/>Dell’uso e dell’attività dell’Arco conduttore nelle contrazioni dei
				<lb/>
				muscoli<emph.end type="italics"/> [6]), di cui ebbi occasione di parlare nelle note alla 2<emph type="sup"/>a<emph.end type="sup"/> delle lettere che
				<lb/>
				vi scrissi nella primavera dell’anno scorso; la qual maniera consiste in fare
				<lb/>
				che i nervi pendenti, o il pezzetto di spina attaccato vadano a toccare le coscie.
			</s>
        </p>
        <p id="N101F9" type="main">
          <s id="N101FB">
				Queste e simili sperienze, ove non interviene alcun conduttore metallico,
				<lb/>
				ossia di quelli che io chiamato avea <emph type="italics"/>eccitatori<emph.end type="italics"/> o <emph type="italics"/>motori<emph.end type="italics"/>; ove una parte dell’ani-<lb/>
				male medesimo fa tutto l’arco conduttore, o se non lo fa tutto, il resto per com-<lb/>
				pire il circolo è fatto da altri deferenti umidi; tali sperienze, gridano i Galva-<lb/>
				niani, sono decisive, perentorie: qui l’elettricità non può ripetersi che dagli
				<lb/>
				organi animali, ne’ quali cioè trovisi il fluido elettrico in istato di carica o di
				<lb/>
				disequilibrio, sbilanciato, come pare, tra i nervi e i muscoli in cui quelli s’im-<lb/>
				piantano, o tra l’interno e l’esterno de’ muscoli medesimi, come ebbe per più
				<lb/>
				probabile l’istesso GALVANI.
			</s>
          <s id="N10219">
				E voi, che ne dite, amico?
			</s>
          <s id="N1021B">
				La date così subito loro
				<lb/>
				vinta?
			</s>
          <s id="N1021F">
				O restate ancora perplesso per le tante altre sperienze da me prodotte,
				<lb/>
				nelle quali è pur manifesto che l’elettricità è meramente artificiale, che il fluido
				<lb/>
				elettrico è mosso da causa estrinseca, per un’azione cioè che risulta dal comba-<lb/>
				ciamento di conduttori dissimili?
			</s>
          <s id="N10227">
				Oppure per far la pace e conciliare le une colle
				<lb/>
				altre sperienze, adottate voi ambidue i principj, e tenete (come opinai anch’io
				<lb/>
				una volta, ma per poco tempo [7]) che quando l’uno e quando l’altro sia la causa
				<lb/>
				delle convulsioni eccitate?
			</s>
          <s id="N1022F">
				Può infatti credersi, che i metalli di specie diversa
				<lb/>
				abbiano realmente nel combaciamento loro CO’ conduttori umidi la virtù di
				<lb/>
				muovere il fluido elettrico, e che ad una tal’azione, alla corrente elettrica
				<lb/>
				quindi eccitata, troppo debole per potersi manifestare co’ segni de’ comuni
				<lb/>
				elettrometri, ma pure più che sufficiente ad irritare i muscoli volontarj, o piut-<lb/>
				tosto i rispettivi nervi, ed altri molto sensibili, per cui passi raccolta, a siffatta
				<lb/>
				corrente abbastanza attiva si risentano le rane anche preparate da lungo tempo,
				<lb/>
				e già molto debilitate, anche le non intieramente preparate, anche senza averne
				<lb/>
				denudati i nervi, e fino i semplici muscoli staccati di esse, o di qualunque ani-<lb/>
				male, e così pure si risentano i nervi del gusto, della visione ec., come ho sco-<lb/>
				perto; anzi non può credersi altrimenti in tante e tante sperienze, nelle quali
				<lb/>
				<pb pagenum="293"/>
				con questo mezzo solamente de’ metalli diversi ottener si possono gli accennati
				<lb/>
				effetti; e può credersi nell’istesso tempo, o sospettarsi almeno, che anche tal-<lb/>
				volta proceda il moto del fluido elettrico da una vera carica o sbilancio negli
				<lb/>
				organi animali, come presumono i Galvaniani, quando cioè si eccitano le con-<lb/>
				vulsioni o con un sol pezzo di metallo, o con due, ma della stessa specie, e fino
				<lb/>
				senza alcun metallo, con un arco cioè di soli conduttori umidi, ossia di 2<emph type="sup"/>a<emph.end type="sup"/> classe,
				<lb/>
				come le novelle sperienze ci mostrano che pur succede talvolta.
			</s>
          <s id="N1025C">
				Quando però
				<lb/>
				si ammetta una tal carica o tensione del fluido elettrico negli organi, dovrà
				<lb/>
				dirsi che sia sommamente debole, e abbia luogo solo per pochissimo tempo,
				<lb/>
				osservandosi che non si eccitano d’ordinario se non convulsioni deboli, e diffi-<lb/>
				cilmente, e solo nelle rane preparate di tutto punto e di fresco, e dotate di
				<lb/>
				somma vitalità.
			</s>
          <s id="N10268">
				Ma infine se basta, come farò vedere e toccar con mano, a
				<lb/>
				spiegare anche queste poche sperienze ambigue il solo principio dell’azione
				<lb/>
				de’ conduttori dissimili, principio dimostrato da tante altre prove sperimentali
				<lb/>
				chiare e parlanti, e senza paragone più numerose, a che ricorrere ad un altro
				<lb/>
				principio supposto, e non provato, di un’elettricità’ cioè propria e attiva degli
				<lb/>
				organi animali?
			</s>
          <s id="N10274">
				Perchè introdurre due principj affatto diversi per fenomeni
				<lb/>
				dell’istesso genere, e del tutto simili? [8]
			</s>
        </p>
        <p id="N10278" type="main">
          <s id="N1027A">
				Dietro queste riflessioni osservando più attentamente, ed analizzando
				<lb/>
				quelle sperienze, in cui mi riusciva di eccitare le convulsioni nella rana con due
				<lb/>
				armature dell’istesso metallo, e fino con un arco di un sol pezzo senz’altra ar-<lb/>
				matura, venni a scoprire che anche picciole accidentali differenze tra dette
				<lb/>
				armature, o tra i due capi dell’arco metallico, nella tempera cioè, nel poli-<lb/>
				mento ecc. bastavano a dar mossa al fluido elettrico, e ad indurre una corrente
				<lb/>
				del medesimo valevole a scuotere la rana compitamente e di fresco preparata:
				<lb/>
				la qual cosa, ch’io avea verificata con moltissime prove sperimentali, fece il
				<lb/>
				soggetto della 1<emph type="sup"/>a<emph.end type="sup"/> delle lettere già mentovate scrittevi l'anno scorso.
			</s>
          <s id="N10292">
				Così poi
				<lb/>
				quando alcuni mesi dopo fu richiamata la mia attenzione alle nuove sperienze
				<lb/>
				del VALLI, in cui non entra metallo di sorta, ripetendo e analizzando anche
				<lb/>
				queste con variarle in più maniere, non tardai molto a riconoscere, che qui
				<lb/>
				pure la diversità de’ conduttori combaciantisi è necessaria; e che tutto il giuoco
				<lb/>
				dipende da questa diversità: e di tale ulteriore scoperta e spiegazione ne feci
				<lb/>
				parte in lettera fin dal principio del passato inverno al Cav.<emph type="sup"/>re<emph.end type="sup"/> BANKS Presi-<lb/>
				dente della Società Reale di Londra, e ad altri miei Corrispondenti; per nulla
				<lb/>
				dire dei molti e nazionali e forastieri, a cui ho mostrate in tutto il corrente
				<lb/>
				anno le sperienze, e che trovandole decisive hanno senza più esitare sottoscritto
				<lb/>
				alla mia opinione.
			</s>
        </p>
        <p id="N102AE" type="main">
          <s id="N102B0">
				Non dubito pertanto, che non siate per soscrivervi ancor voi, Collega ama-<lb/>
				tissimo, qualunque sia stato fino ad ora il vostro sentimento, sol che pesiate
				<lb/>
				bene le ragioni, e più le sperienze, che con maggior ampiezza di quello ho fatto
				<lb/>
				con altri vado ad esporvi, e vi piaccia di ripeterle voi medesimo.
			</s>
        </p>
        <pb pagenum="294"/>
        <p id="N102BA" type="main">
          <s id="N102BC">
				Quest’ultimo oso dire è necessario: non basta leggere o sentire da altri le
				<lb/>
				descrizioni, bisogna vedere le sperienze, farle, rifarle, cambiando forma e ma-<lb/>
				niera, come ho praticato io, per ritrarne una perfetta convinzione [9].
			</s>
        </p>
        <p id="N102C2" type="main">
          <s id="N102C4">
				Non sarà inutile prima di tutto, ch’io mi trattenga un poco a farvi più
				<lb/>
				da proposito osservare quello, che di passaggio ho già toccato, cioè che non
				<lb/>
				sempre, e a mala pena, anche nelle rane preparate di tutto punto, e solo per
				<lb/>
				poco tempo riescono le vantate sperienze delle convulsioni eccitatevi senza
				<lb/>
				l’intervento di alcun metallo, come avrete diggià voi medesimo provato;
				<lb/>
				laddove coll’applicazione di due conduttori metallici assai diversi, ed anche di
				<lb/>
				un solo metallo interposto però a due conduttori non metallici molto pure di-<lb/>
				versi fra loro (che è un secondo mezzo da me scoperto poco meno efficace del
				<lb/>
				primo [10]) non si manca mai di ottenere le convulsioni incomparabilmente più
				<lb/>
				forti, e per assai più lungo tempo, e sì anche nelle rane intiere, o preparate
				<lb/>
				per metà, cioè sviscerate soltanto.
			</s>
          <s id="N102DA">
				Son dunque ben poco efficaci tutti que’ mezzi
				<lb/>
				in cui non si adoprano gli eccitatori metallici, se è assolutamente necessario
				<lb/>
				per ottener qualche cosa, che la rana sia preparata nella miglior maniera possi-<lb/>
				bile, in guisa cioè che le gambe tengano al tronco per i soli nervi ischiatici, e
				<lb/>
				preparata così di fresco, e piene le sue membra di vitalità; e se non sempre si
				<lb/>
				ottengono le convulsioni neppure con tale perfetta preparazione, e le altre fa-<lb/>
				vorevoli circostanze, anzi solo rarissime volte nella maggior parte de’ sopra
				<lb/>
				descritti modi.
			</s>
        </p>
        <p id="N102EA" type="main">
          <s id="N102EC">
				Più spesso è vero, e per più lungo tempo si ottengono nella maniera de-<lb/>
				scritta per la prima, che è di ripiegare una delle gambe della rana, e addurla
				<lb/>
				al contatto o de’ detti nervi ischiatici, pe’ quali restano esse gambe attaccate
				<lb/>
				al tronco, o di una parte qualunque carnosa del tronco medesimo; non però
				<lb/>
				sempre neppure nelle rane più vivaci, e ne’ primi momenti dopo la dissezione,
				<lb/>
				che sono i più favorevoli: non sempre, dico, si ottengono le convulsioni neppure
				<lb/>
				adoperando in questa maniera: e se si osserveranno le circostanze, nelle quali
				<lb/>
				suol succedere, e quelle in cui non succede mai, o quasi mai l’esperienza, si
				<lb/>
				verranno facilmente a scoprire le condizioni richieste al riuscimento; e queste
				<lb/>
				condizioni ci faran conoscere finalmente la causa vera di tali fenomeni, il prin-<lb/>
				cipio generale da cui dipendono.
			</s>
        </p>
        <p id="N10302" type="main">
          <s id="N10304">
				Queste condizioni sono dunque:
			</s>
        </p>
        <p id="N10306" type="main">
          <s id="N10308">
				1° Che il corpo della rana trucidata, scorticata, e finita di preparare,
				<lb/>
				non sia già deterso e netto, come sarebbe lavato nell’acqua, ma anzi sporco,
				<lb/>
				imbrattato in parte almeno di sangue, o di altro umore più o men viscido e
				<lb/>
				tegnente: la qual circostanza, delle membra cioè lorde di sangue si accenna di
				<lb/>
				passaggio dall’istesso Dr. VALLI.
			</s>
          <s id="N10312">
				In difetto giova intridere a bella posta quella
				<lb/>
				parte della gamba, de’ nervi, o del tronco, ove ha da succedere in appresso
				<lb/>
				il combaciamento ossia mutuo contatto, con scialiva, come ha notato l’anzi-<lb/>
				<pb pagenum="295"/>
				detto autore, con acqua salata
				<note n="b">
				<p id="N10320" type="main">
					<s id="N10323">
						Anche nelle sperienze oppostemi nell’operetta sopracitata <emph type="italics"/>Dell’uso e dell’attività
						<lb/>
						dell’Arco conduttore<emph.end type="italics"/> ec., delle quali ho reso conto nella nota 4 della lettera 2<emph type="sup"/>a<emph.end type="sup"/>, accenna l'Au-<lb/>
						tore anonimo, che succede molto più facilmente di veder eccitate le convulsioni nell’atto che
						<lb/>
						il picciol troncone di spina pendente dai nervi ischiatici si porta a toccare le nude coscie,
						<lb/>
						ore siano state queste per qualche tempo in un bagno di acqua salata e se ne trovino inzup-<lb/>
						pate.
					</s>
					<s id="N1033C">
						Or dunque non mi attengo più alla spiegazione ch’ivi ho cercato di dare, ricorrendo
						<lb/>
						cioè ad un’irritazione meccanica per via di urto o pressione qualsiasi, spiegazione di cui non
						<lb/>
						mi trovava neppur allora soddisfatto pienamente, e colla quale non si può render ragione al-<lb/>
						cuna del come e perchè l’acqua salata ed altri liquori contribuiscano tanto alla riuscita di
						<lb/>
						tali sperienze; ma riduco sì queste che le altre analoghe ad un’azione sopra il fluido elet-<lb/>
						trico che esercitino anche i conduttori non metallici, sebbene incomparabilmente più debole,
						<lb/>
						in virtù del mutuo combaciamento, ove siano pure codesti conduttori ed eccitatori a para-<lb/>
						gon de’ metalli imperfettissimi, tra loro diversi: come verrò spiegando.
					</s>
				</p>
			</note>
			, con orina, con muco, con diversi succhi ecc.,
			<lb/>
			o meglio con sapone stemperato in poca acqua, o assai meglio ancora con li-<lb/>
			quori acidi od alcalini concentrati, come ho trovato io nel moltiplicare e va-<lb/>
			riare in mille modi codeste, sperienze, e come vi sarà facile di verificare.
		</s>
        </p>
        <p id="N10355" type="main">
          <s id="N10357">
			2° Che il contatto de’ nudi nervi ischiatici, e de’ nudi muscoli del tronco
			<lb/>
			si faccia, non da qualsivoglia parte della gamba, ma dal tendine in cui termina
			<lb/>
			il muscolo grosso della gamba, ossia il gastrocnemio, il qual tendine o ligamento
			<lb/>
			passando sopra l’articolazione del piede si prolunga fino alle dita [11], e compare
			<lb/>
			scoperto per tutto quel tratto.
		</s>
          <s id="N10361">
			È cosa veramente curiosa il vedere come addu-<lb/>
			cendo al contatto de’ muscoli dorsali anche intrisi di sangue o di altro umore
			<lb/>
			viscido o salino, i muscoli delle coscie, niente di ordinario succede; e niente pure
			<lb/>
			facendo a quelli combaciare l’istesso muscolo gastrocnemio al disopra della
			<lb/>
			sua metà, cioè per tutta quella parte ch’esso si mostra puramente carnoso,
			<lb/>
			e che all’incontro facendolo toccare al disotto, cioè per la parte in cui il muscolo
			<lb/>
			medesimo degenera in sostanza tendinosa, e presenta una superficie bianchiccia
			<lb/>
			di un lucido di perla, nascono le convulsioni.
		</s>
          <s id="N10371">
			Convien dunque imprimere sopra
			<lb/>
			i muscoli del tronco, o sopra i nervi ischiatici l’estremità di detto muscolo
			<lb/>
			gastrocnemio, o l’articolazione del piede, o il resto ove compar fuori il gran
			<lb/>
			tendine, cioè portare al detto combaciamento qualche punto di quel lungo
			<lb/>
			tratto bianco, e non altrimenti, se ottener si vogliono le convulsioni: le quali
			<lb/>
			neppure con ciò si ottengono sempre, anzi non mai, o quasi mai, se anche l’altra
			<lb/>
			condizione non vi si ritrova, cioè dell’umor viscido o salino interposto.
		</s>
        </p>
        <p id="N1037F" type="main">
          <s id="N10381">
			In prova di che, se lavisi ben bene la rana preparata con acqua netta,
			<lb/>
			non servirà più a nulla neppure il contatto fatto sopra i muscoli dorsali colle
			<lb/>
			parti tendinose bianche della gamba.
		</s>
          <s id="N10387">
			Che se pure succeda alcune volte di ecci-<lb/>
			tare così delle convulsioni anche dopo tal lavatura, si può credere, che tuttor
			<lb/>
			vi sia dell’umore eterogeneo aderente: infatti quando dopo aver lavata la
			<lb/>
			<pb pagenum="296"/>
			rana una sol volta, e per poco tempo, mi è succeduto per accidente di poter
			<lb/>
			ancora eccitarvi le convulsioni nel modo indicato, non le ottenni più dopo una
			<lb/>
			seconda lavatura più accurata, in cui venni stropicciando bene le parti, massime
			<lb/>
			il dorso, e i contorni delle ferite.
		</s>
        </p>
        <p id="N10398" type="main">
          <s id="N1039A">
			Vi vogliono dunque ambedue le condizioni, e dell’umore eterogeneo in-<lb/>
			terposto, e dell’eterogeneità, dirò così, delle parti animali che si affacciano, che
			<lb/>
			non siano cioè quest’e troppo simili, come muscolo e muscolo, massime d’eguale
			<lb/>
			struttura e consistenza, ma differiscano anzi notabilmente; e la differenza che
			<lb/>
			trovo più conducente è quella appunto tra tendine e muscolo o tra tendine e
			<lb/>
			nervo (quella tra muscolo e nervo non lo è tanto); siccome la differenza, che
			<lb/>
			fa meglio tra questi conduttori animali, e il terzo che dee trovarsi ad essi in-<lb/>
			terposto nel venire al contatto, e compiersi il circolo, è che questo terzo corpo
			<lb/>
			preso di mezzo sia un umore viscido o salino, o meglio sapone stemperato,
			<lb/>
			o meglio ancora alcali reso appena liquido, come già ho indicato.
		</s>
        </p>
        <p id="N103AE" type="main">
          <s id="N103B0">
			Or queste circostanze e condizioni richieste all’uopo di destare le convul-<lb/>
			sioni nelle rane puntualmente preparate senza l’intervento di alcun metallo,
			<lb/>
			o conduttore della 1<emph type="sup"/>a<emph.end type="sup"/> classe, bastano già a mostrare, che non procede dunque
			<lb/>
			la corrente del fluido elettrico eccitatrice di tali convulsioni da alcuna scarica
			<lb/>
			o mossa data al fluido dagli organi animali; giacchè per qual ragione succede-<lb/>
			rebbe siffatta scarica soltanto portando al contatto dei muscoli del tronco,
			<lb/>
			o dei nervi ischiatici le parti tendinose della gamba, e in niun modo facendovi
			<lb/>
			toccare nella stessa foggia le parti muscolari ossia le carnose e molli dell’istessa
			<lb/>
			gamba, o delle coscie, quando il circolo conduttore sarebbe in questo caso com-<lb/>
			pito egualmente, ed egualmente atto, anzi meglio, per essere più corto, e per
			<lb/>
			essere quelle parti appunto perchè più molli e succose, più deferenti che il
			<lb/>
			duro tendine, e men umido?
		</s>
          <s id="N103CE">
			E per qual ragione ancora non succederebbe, fa-<lb/>
			cendosi il contatto immediato di qualsisia parte della gamba coi muscoli dor-<lb/>
			sali, senza l’interposizione di un terzo corpo deferente diverso dall’una e dal-<lb/>
			l’altra sostanza animale, e diverso dall’umor acqueo, senza l’interposizione,
			<lb/>
			dico, di un umor glutinoso e salino?
		</s>
          <s id="N103D8">
			E non dovrebbe anzi succedere assai
			<lb/>
			meglio coll’applicazione immediata della gamba ai muscoli dorsali, che frap-<lb/>
			ponendosi tal terzo corpo, il quale ben lungi dal rendere più facile e spiccia
			<lb/>
			la via conduttrice già alquanto resistente per essere le istesse sostanze e umori
			<lb/>
			animali deferenti non del tutto perfetti, non può che renderla vieppiù resistente,
			<lb/>
			sendo esso pure che si trammezza un conduttore imperfetto?
		</s>
          <s id="N103E4">
			Or come dunque
			<lb/>
			moltiplicando i conduttori imperfetti, formando l’arco di tre di questi invece
			<lb/>
			di due, si faciliterebbe la supposta scarica e tragitto del fluido elettrico?
		</s>
          <s id="N103EA">
			Come
			<lb/>
			anzi in questo modo solamente avrebbe luogo essa scarica e tragitto, tale al-<lb/>
			meno da convellere la rana, e non nell’altro modo, del contatto cioè immediato
			<lb/>
			della gamba, che pur dovrebbe essere più adatto?
		</s>
        </p>
        <p id="N103F2" type="main">
          <s id="N103F4">
			Se ciò, come vedesi, è un paradosso inesplicabile stando alle idee che ab-<lb/>
			<pb pagenum="297"/>
			biamo delle cariche elettriche, e de’ conduttori considerati semplicemente come
			<lb/>
			tali, ossia come corpi permeabili al fluido elettrico, e non altro; se, dico, non
			<lb/>
			possono conciliarsi in alcun modo con queste idee, anzi si contraddicono mani-<lb/>
			festamente gli enunciati fenomeni, convien dunque ricorrere ad altri principj,
			<lb/>
			e abbandonata tal supposizione di carica o sbilancio qualsiasi di fluido elet-<lb/>
			trico ne’ nervi e muscoli della nostra rana preparata, considerare i conduttori,
			<lb/>
			di cui si tratta, sotto un altro aspetto, riguardarli cioè al dippiù come <emph type="italics"/>eccita-<lb/>
			tori<emph.end type="italics"/> o <emph type="italics"/>motori<emph.end type="italics"/>, val a dire dotati della maravigliosa virtù di concitare il fluido
			<lb/>
			elettrico, impellerlo, smuoverlo, tosto che vengano al contatto, e si combacino
			<lb/>
			alcuni tra di loro di diversa specie, come appunto nelle sperienze testè descritte.
		</s>
          <lb/>
          <s id="N1041A">
			Volgete e rivolgete la cosa in tutti gli aspetti, quest’è l’unica maniera di spie-<lb/>
			gare tali sperienze, ed infinite altre, che si riducono al medesimo principio,
			<lb/>
			come farò vedere.
		</s>
        </p>
        <p id="N10420" type="main">
          <s id="N10422">
			Ma che? saranno anche i conduttori non metallici, i conduttori liquidi,
			<lb/>
			o contenenti in qualsisia modo umore, che chiamo conduttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe,
			<lb/>
			saranno anch'essi combinati fra loro soli, eccitatori, come lo sono i metalli con-<lb/>
			duttori di 1<emph type="sup"/>a<emph.end type="sup"/> classe combinati assieme a quelli di 2<emph type="sup"/>a<emph.end type="sup"/>?
		</s>
          <s id="N1043C">
			Godranno anche tali con-<lb/>
			duttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe dell’istessa virtù?
		</s>
          <s id="N10446">
			Sì certo; ma in grado molto inferiore,
			<lb/>
			cedendo per tal riguardo ai conduttori metallici, come cedono loro anche ri-<lb/>
			spetto a tal facoltà conduttrice.
		</s>
          <s id="N1044C">
			Io ebbi queste idee fin dal principio, e le
			<lb/>
			spiegai ad alcuni amici e corrispondenti, fra’ quali al sig. Abate TOMMASELLI
			<lb/>
			di Verona, e al Dr. VAN MARUM celebre Fisico Olandese in alcune lettere scritte
			<lb/>
			nell’estate del 1792; dall’una o dall’altra delle quali vi ricopierò qualche squarcio
			<lb/>
			a pie’ di pagina, acciò vediate s’io non inclinava a credere, e tenea quasi per
			<lb/>
			fermo, che anche nel combaciamento de’ conduttori umidi, ossia di 2<emph type="sup"/>a<emph.end type="sup"/> classe,
			<lb/>
			sol che fosser diversi fra loro, veniva dato impulso al fluido elettrico, non altri-<lb/>
			menti che nel combaciamento de’ metalli, o conduttori di 1<emph type="sup"/>a<emph.end type="sup"/> classe coi detti
			<lb/>
			umidi
			<note n="c">
			<p id="N1046D" type="main">
				<s id="N10470">
					Nella lettera all’Ab. TOMMASELLI io mi spiegava ne’ seguenti termini: « Son dunque
					<lb/>
					« i metalli non solo conduttori perfetti, ma <emph type="italics"/>motori<emph.end type="italics"/> dell’elettricità; non solo prestano essi la
					<lb/>
					« via facilissima al passaggio del fluido elettrico, che trovandosi già sbilanciato tenda a por-<lb/>
					« tarsi dal luogo in cui sovrabbonda a quello che rispettivamente ne scarseggia; ma van pro-<lb/>
					« ducendo essi stessi e promovendo un tal quale sbilancio, con estrarre di esso fluido od in-<lb/>
					« tradurne dove pur trovasi in giusta dose ripartito; e ciò col solo stare applicati a qualsiasi
					<lb/>
					« altro conduttore, non altrimenti che avviene collo stropicciamento degli idioelettrici; e
					<lb/>
					« siccome tal metallo prevale sopra tal altro nel tirare il fluido o nel rilasciarlo; così avviene
					<lb/>
					« che due armature di diverso metallo, applicate come si è detto, se comunichino fra loro lo
					<lb/>
					« mettano in un perpetuo giro... Ella è questa una nuova virtù de’ metalli da nessuno ancora
					<lb/>
					« sospettata, che le mie sperienze mi hanno condotto ad iscoprire ».
				</s>
				<s id="N1048D">
					Or fate attenzione a quello,
					<lb/>
					ce immediatamente soggiungo: « Nè però io penso, che sia essa propria soltanto de’ metalli,
					<lb/>
					« ma bene di <emph type="italics"/>tutti i conduttori<emph.end type="italics"/>; e tengo debba stabilirsi per legge generale, che il semplice con-<lb/>
					« tatto o combaciamento di conduttori di diversa superficie, e di qualità soprattutto diversa,
					<lb/>
					« basta a turbare in qualche modo l’equilibrio del fluido elettrico, e a smuoverlo, senza cioè
					<lb/>
					« che siavi bisogno di stropicciamento alcuno: il quale stropicciamento, siccome pure il per-<lb/>
					« cuotere, ed anche il sol premere, non per altro riescono tanto più efficaci, che perchè dan
					<lb/>
					«luogo a miglior combaciamento delle superficie, adducendo un più gran numero di punti
					<lb/>
					« a un più perfetto contatto ».
				</s>
				<lb/>
				<s id="N104A8">
					Ciò che qui viene da ultimo semplicemente indicato riguardo all’essere verosimilmente
					<lb/>
					l’istesso principio, l’istessa virtù cioè che si dispiega pel combaciamento di corpi diversi, la
					<lb/>
					causa tanto dell’elettricità conosciuta, che s’induce a forza di stropicciare un contro l’altro
					<lb/>
					due idioelettrici, od un idioelettrico e un conduttore, quanto di quella ultimamente sco-<lb/>
					pertasi e meno apparente, mossa da’ semplici contatti di soli conduttori, l’ho poi spie-<lb/>
					gato con qualche maggiore ampiezza nella lunga lettera al Dr. VAN MARUM, e cercherò di
					<lb/>
					porlo vieppiù in chiaro un’altra volta.
				</s>
			</p>
		</note>
		.
	</s>
          <s id="N104B9">
		Senza abbandonare del tutto tali idee mi spiegai in seguito qualche
		<lb/>
		<pb pagenum="298"/>
		volta diversamente, non tanto perchè credessi che nulla realmente fosse l’azione
		<lb/>
		sul fluido elettrico de’ conduttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe combaciantisi fra loro, comunque
		<lb/>
		diversi, e che in niun modo godessero della virtù eccitatrice; quanto perchè
		<lb/>
		stimai si meschina tal loro virtù ed azione, sì picciola e languida la corrente
		<lb/>
		elettrica che si potrebbe con essi soli indurre, da non riuscir valevole ad ecci-<lb/>
		tare le contrazioni nella rana neppure la più vivace e meglio preparata.
	</s>
          <s id="N104D0">
		Non
		<lb/>
		debbonsi dunque intendere a rigore alcune espressioni, e come dove nella 2<emph type="sup"/>a<emph.end type="sup"/>
		<lb/>
		delle lettere scrittevi l’anno scorso ho avanzato: « che l’arco conduttore for-<lb/>
		« mato da una o più persone, da cuoi, panni, cartoni, o corpi bagnati quali essi
		<lb/>
		« sieno, da deferenti insomma non metallici, nulla più essendo atto a prestare
		<lb/>
		« che l’officio appunto di conduttore, non può determinare alcuna corrente
		<lb/>
		« di esso fluido, che invada i nervi e muscoli dell’animale, e ne gli irriti e scuota ».
	</s>
          <lb/>
          <s id="N104E5">
		Non debbe dico intendersi quello che ivi si avanza a tutto rigore, cioè che nulla
		<lb/>
		affatto sia l’azione nel mutuo combaciamento di tali conduttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe
		<lb/>
		anche i più diversi; ma bene esser quella un’azione così da poco, che può quasi
		<lb/>
		aversi per nulla.
	</s>
          <s id="N104F3">
		Che se pure volli dire che fosse nulla del tutto, e pensai un mo-<lb/>
		mento così; troppo m’allontanai, come si vede, dalle idee che ebbi per lungo
		<lb/>
		tempo; e alle quali fui tosto richiamato dalle sperienze qui innanzi descritte
		<lb/>
		del VALLI, ed altre di questo genere da me intraprese: nè picciola fu la compia-<lb/>
		cenza in vedere così verificate le antiche mie congetture, colle quali generaliz-<lb/>
		zando il principio, che pel semplice combaciamento di conduttori diversi si
		<lb/>
		toglie dal riposo il fluido elettrico, si concita e smuove, non altrimenti che per
		<lb/>
		la confricazione, tantochè se il circolo conduttore è compito si determina
		<lb/>
		ad una corrente continua, io attribuiva qualche poco di cotesta virtù eccita-<lb/>
		trice anche ai conduttori non metallici, qualunque fossero, purchè s’incontras-<lb/>
		sero dissimili nel combaciamento.
	</s>
          <s id="N10509">
		Dico <emph type="italics"/>qualche poco<emph.end type="italics"/> di virtù, avendola sempre
		<lb/>
		creduta, e credendola tuttora di molto inferiore a quella che manifestasi nel
		<lb/>
		combaciamento di uno di tai conduttori non metallici, o di 2<emph type="sup"/>a<emph.end type="sup"/> classe, con due
		<lb/>
		metallici, o di 1<emph type="sup"/>a<emph.end type="sup"/> classe fra loro pure diversi.
	</s>
        </p>
        <pb pagenum="299"/>
        <p id="N10525" type="main">
          <s id="N10527">
		Ad ogni modo non può più dirsi essere tanto debole, che l’effetto ne sia
		<lb/>
		sempre insensibile, conforme stimai in addietro, ora che impariamo da nuove
		<lb/>
		sperienze, come in alcuni casi, nelle circostanze cioè e condizioni sopra spie-<lb/>
		gate, si eccita tal corrente elettrica, che giunge a destare delle convulsioni in
		<lb/>
		una rana perfettamente e di fresco preparata: a produrre il qual effetto per
		<lb/>
		altro ci vuole pochissimo, un nulla quasi; come si può provare colle scariche
		<lb/>
		elettriche comuni, segnatamente delle boccie di Leyden, bastando le più de-<lb/>
		boli, incapaci non che a dar la menoma scintilla, ma a movere alcun poco il
		<lb/>
		più delicato elettrometro [12], quello di BENNET a listerelle di foglia d’oro da
		<lb/>
		voi perfezionato.
	</s>
        </p>
        <p id="N1053B" type="main">
          <s id="N1053D">
		Ci vuole ancor poco assai, sebben ci voglia quattro o cinque volte dippiù,
		<lb/>
		a scuotere la rana non del tutto preparata, ma scorticata e sventrata in guisa
		<lb/>
		che compaiano i nervi ischiatici, senza però recidere le parti di dietro su cui
		<lb/>
		riposano; tanto poco ci vuole, che basta ancora per eccitare le convulsioni in
		<lb/>
		cotesta rana, che diremo mezza preparata, la carica di una boccia che non
		<lb/>
		move, o move appena un elettrometro sensibilissimo [13]; e similmente basta
		<lb/>
		la corrente elettrica eccitata e indotta dal semplice accozzamento di tre con-<lb/>
		duttori diversi, de’ quali uno o due siano metallici, ossia di 1<emph type="sup"/>a<emph.end type="sup"/> classe; ove
		<lb/>
		cioè od un conduttore umido, un conduttore di 2<emph type="sup"/>a<emph.end type="sup"/> classe trovisi interposto a
		<lb/>
		due di 1<emph type="sup"/>a<emph.end type="sup"/> molto diversi tra loro; od al rovescio uno di 1<emph type="sup"/>a<emph.end type="sup"/> classe trovisi frap-<lb/>
		posto a due di 2<emph type="sup"/>a<emph.end type="sup"/> molto pure diversi, (intorno alla quale seconda maniera,
		<lb/>
		accennata qui soltanto, mi riservo a trattenervi un’altra volta più a lungo).
	</s>
        </p>
        <p id="N10573" type="main">
          <s id="N10575">
		Dico <emph type="italics"/>molto diversi<emph.end type="italics"/>, perchè, se qualunque anche picciola diversità, sia dei
		<lb/>
		due conduttori di 1<emph type="sup"/>a<emph.end type="sup"/> classe, sia dei due di 2<emph type="sup"/>a<emph.end type="sup"/>, interpolati rispettivamente da
		<lb/>
		uno dell’altra classe, può in alcune circostanze bastare all’uopo; se quella de-<lb/>
		bolissima corrente di fluido elettrico, che s’induce in virtù di siffatti accozza-<lb/>
		menti può eccitare le convulsioni nelle gambe della rana compitamente prepa-<lb/>
		rata, in guisa cioè che pe’ soli nervi crurali debba passare tutta ristretta tal
		<lb/>
		corrente; non è già valevole ad eccitarle nella rana sol mezzo preparata, in cui
		<lb/>
		minor parte di essa corrente passa pe’ detti nervi, più larga via presentandole
		<lb/>
		le annesse parti, egualmente, se non più ancora, umide e deferenti: conviene
		<lb/>
		quindi in tal caso per ottenere l’effetto, che sia non così debole e meschina la
		<lb/>
		corrente elettrica, ma alquanto più copiosa o più forte (sebbene non ancor tanto
		<lb/>
		da darne segno i comuni elettrometri anche più sensibili), quale si eccita sol-<lb/>
		tanto ove o i due conduttori di 1<emph type="sup"/>a<emph.end type="sup"/> classe interpolati da uno di 2<emph type="sup"/>a<emph.end type="sup"/>, o i due di 2<emph type="sup"/>a<emph.end type="sup"/>
		<lb/>
		interpolati da uno di 1<emph type="sup"/>a<emph.end type="sup"/>, come si è indicato, siano un dall’altro assai diversi.
	</s>
        </p>
        <p id="N105BB" type="main">
          <s id="N105BD">
		Ma coll’accozzamento di tre conduttori tutti della 2<emph type="sup"/>a<emph.end type="sup"/> classe, o conduttori
		<lb/>
		umidi, escluso cioè dal circolo ogni metallo, miniera, pirite, carbone, ogni con-<lb/>
		duttore insomma di 1<emph type="sup"/>a<emph.end type="sup"/> classe, con quei soli di 2<emph type="sup"/>a<emph.end type="sup"/> quanto si voglia diversi, in-<lb/>
		trecciati e applicati in qualunque modo, non ho potuto mai ottenere la più
		<lb/>
		piccola convulsione o sbattimento nella rana preparata soltanto a metà;
		<lb/>
		<pb pagenum="300"/>
		molto meno è possibile ottenerle in una rana, che non sia neppure sventrata (nel
		<lb/>
		qual caso vi vuole una forza elettrica otto o dieci volte ancora maggiore, come
		<lb/>
		ho trovato colle scariche de’ conduttori della macchina, delle boccie ecc. [14]),
		<lb/>
		molto meno in un membro, o muscolo staccato dalla medesima, o da altro
		<lb/>
		animale, se tal membro o muscolo non è preparato in maniera, che il nervo
		<lb/>
		inserviente al moto sia snudato, e ne penda fuori tutto libero intorno, ecc,;
		<lb/>
		laddove le ottengo facilmente in cotali membri e muscoli spogliati appena degli
		<lb/>
		integumenti, senza cioè scoprire e mettere a nudo alcun nervo, e fino nelle
		<lb/>
		rane, anguille, ecc., intiere e intatte, ottengo, dico, delle forti contrazioni mu-<lb/>
		scolari, e moto violento de’ membri impiegando due metalli molto diversi [15],
		<lb/>
		e. g. argento e piombo, o meglio argento e foglio stagnato, o meglio ancora
		<lb/>
		argento e zinco, ed applicandoli o immediatamente uno ad una parte, l’altro
		<lb/>
		all’altra di quel tal’animale, di quel tal membro o muscolo, o coll’interposizione
		<lb/>
		d’altri conduttori umidi ossia di 2<emph type="sup"/>a<emph.end type="sup"/> classe; ed anche con un solo metallo o con-<lb/>
		duttore di 1<emph type="sup"/>a<emph.end type="sup"/> classe ottengo gli stessi moti, segnatamente col zinco interponen-<lb/>
		dolo a due conduttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe molto diversi, come all’acqua da una parte
		<lb/>
		o ad un corpo qualunque imbevuto d’umor acquoso, e dall’altra a un forte
		<lb/>
		liquor acido od alcalino.
	</s>
          <s id="N10612">
		Ma di quest’ultima maniera, in cui interviene un solo
		<lb/>
		conduttore di 1<emph type="sup"/>a<emph.end type="sup"/> classe, ho già detto che mi riservo a parlare più lungamente
		<lb/>
		un’altra volta.
	</s>
          <s id="N1061E">
		Qui consideriamo le combinazioni, in cui non ne entra nessuno
		<lb/>
		di detta 1<emph type="sup"/>a<emph.end type="sup"/> classe nel circolo de’ conduttori, e conchiudiamo dal fin qui detto,
		<lb/>
		che se l’azione sul fluido elettrico nell’accozzamento di tre tutti della 2<emph type="sup"/>a<emph.end type="sup"/> classe,
		<lb/>
		comunque diversi tra loro, non può dirsi che sia sempre senza effetto sen-<lb/>
		sibile, è però debolissima, e incomparabilmente meno efficace di quella che ri-<lb/>
		sulta per l’intreccio di due di una classe, ed uno dell’altra diversi molto tra
		<lb/>
		loro.
	</s>
        </p>
        <p id="N10638" type="main">
          <s id="N1063A">
		Ed ecco così generalizzato il principio, che in ogni combaciamento di con-<lb/>
		duttori diversi nasce un’azione, che dà mossa più o meno al fluido elettrico,
		<lb/>
		tantochè ove compiasi il circolo da tre appunto quali essi sieno, purchè diversi,
		<lb/>
		una qualche corrente, o mediocre, o debole, o debolissima di esso fluido viene
		<lb/>
		sempre incitata.
	</s>
          <s id="N10644">
		Inerendo al quale principio, o legge generale da me scoperta,
		<lb/>
		e che tutto concorre a stabilire, invece di restringerci a dire, come per lo pas-<lb/>
		sato, che il fluido elettrico è messo in corrente ogniqualvolta due conduttori
		<lb/>
		metallici diversi comunicando fra loro o immediatamente o per altri metalli,
		<lb/>
		combaciano e prendon di mezzo uno o più conduttori umidi, ossia della 2<emph type="sup"/>a<emph.end type="sup"/> classe,
		<lb/>
		continui; diremo semplicemente e in generale : ogniqualvolta uno o più condut-<lb/>
		tori continui di questa 2<emph type="sup"/>a<emph.end type="sup"/> classe s’interpongono a due diversi e tra loro, e col
		<lb/>
		corpo che combaciano; lasciando fuori il termine <emph type="italics"/>metallici<emph.end type="italics"/>, che pone una certa
		<lb/>
		limitazione non troppo giusta, oppure cambiando le parole <emph type="italics"/>conduttori metal-<lb/>
		lici diversi<emph.end type="italics"/> in <emph type="italics"/>conduttori diversi, massime metallici<emph.end type="italics"/>, o di 1<emph type="sup"/>a<emph.end type="sup"/> classe; col quale <emph type="italics"/>mas-<lb/>
		sime<emph.end type="italics"/> e si conserva la prerogativa, che fin nelle prime Memorie ho attribuita
		<lb/>
        <pb/>
        <pb/>
		<pb pagenum="301"/>
		a tali conduttori di 1<emph type="sup"/>a<emph.end type="sup"/> classe, di essere cioè eccitatori, o motori che dir si voglia,
		<lb/>
		per eccellenza; e l’istessa virtù in grado molto inferiore si concede pur anche
		<lb/>
		a quelli di 2<emph type="sup"/>a<emph.end type="sup"/> classe, come fu già mio pensiero, e come viene finalmente dimo-<lb/>
		strato, che la possiedono diffatti, ma appunto debole assai, dalle sperienze
		<lb/>
		sopra addotte; intorno alle quali mi propongo di trattenervi ancora in un’altra
		<lb/>
		lettera [16], che seguirà dappresso la presente.
	</s>
        </p>
        <p id="N1069F" type="main">
          <s id="N106A1">
		Scrivo da Como, e nell’ozio delle vacanze, che stanno per terminare; onde difficil-<lb/>
		mente potrò spedire l’altra lettera prima di restituirmi a Pavia, che sarà verso S. Martino.
	</s>
          <lb/>
          <s id="N106A6">
		Aspetto con desiderio sue righe, che mi spieghino il sentimento suo sopra la materia in
		<lb/>
		questione, e mi diano altre nuove letterarie, e in particolare delle sue studiose ricerche.
	</s>
        </p>
        <p id="N106AA" type="main">
          <s id="N106AC">
		Io ho continuato ad occuparmi molto intorno ai vapori elastici, e sono stato condotto
		<lb/>
		ad alcuni bei ritrovati consentanei molto alla teoria di DE LUC: p. e. che la quantità del va-<lb/>
		pore è la stessa in uno spazio vuoto o pieno d’aria, rara o densa, e dipende unicamente dal
		<lb/>
		grado di calore; onde cade affatto la teoria della dissoluzione de’ vapori nell’aria; che la forza
		<lb/>
		del vapore, ossia la pressione che esso equilibra, cresce in una progressione geometrica cre-<lb/>
		scendo il calore in una progressione aritmetica: che tal progressione geometrica è come 1, 2,
		<lb/>
		4 ecc. crescendo il calore di 16 in 16 gradi circa; cosicchè essendo la pressione del vapor acqueo
		<lb/>
		eguale a 13 pollici di mercurio alla temperatura di 64 gradi Reaumur, divenendo eguale a
		<lb/>
		28 pollici a gr. 80, cioè crescendo di 15 poll., cresce poi di 30 poll. e arriva a 58 alla tempera-<lb/>
		tura di 96 gradi ecc. : che questa stessa progressione in ragion dupla di 16 in 16 gradi ha luogo
		<lb/>
		come pel vapor acqueo, così per ogni altro vapore elastico, dello sp. di vino, dell’etere ecc.
		<lb/>
		la differenza stando solo nel grado di calore richiesto a produrre il vapore di tal densità e
		<lb/>
		forza elastica, che equilibri una data pressione, p. e. quella di 28 poll. di mercurio (giugnendo
		<lb/>
		al qual termine circa bolle il liquido ne’ vasi aperti, come si sa).
	</s>
          <s id="N106C8">
		Or dunque essendo la tempe-<lb/>
		ratura richiesta all’indicata forza del vapore, 80 gradi per quello dell’acqua, 65 per quello
		<lb/>
		dell’alcool, e 31 per quello dell’etere vitriolico, diminuirà egualmente in tutti essa forza o
		<lb/>
		pressione di poll. 15, e ridurrassi quindi a 13, ove scemi la rispettiva temperatura di 16 gr.,
		<lb/>
		cioè riducasi a 64 gr. il vapor acqueo, a 49 quello dell’alcool, a 15 quello dell’etere; e simil-<lb/>
		mente crescerà in tutti di 30 poll., arrivando a 58, se invece s’innalzi la rispettiva tempera-<lb/>
		tura di 16 gr. portandola pel vapor acqueo a 96, per quello dell’alcool a 81, per quello del-<lb/>
		l’etere a 47 ecc.
	</s>
          <s id="N106D8">
		Per tali sperienze sopra i vapori ho immaginati e costrutti varj apparati, che
		<lb/>
		meritano d’essere descritti; e lo farò pubblicando alcune Memorie su questa materia bellis-<lb/>
		sima e importantissima, ohe ho già abbozzato. ma che non SO quando potrò terminare.
	</s>
        </p>
        <p id="N106DE" type="main">
          <s id="N106E0">
		Sono colla maggior stima
	</s>
        </p>
      </chap>
    </body>
    <back>
      <section type="editorcomment">
        <pb/>
        <p id="N106E6" type="main">
          <s id="N106E8">
				<emph type="italics"/>NOTE DELLA COMMlSSIONE <emph.end type="italics"/>
				<lb/>
				ED AGGIUNTE TRATTE DAI MANOSCRITTI DI A. VOLTA
			</s>
        </p>
        <p id="N106F2" type="main">
          <s id="N106F4">
				[1] <emph type="italics"/>In Cart. Volt. J 32 a questo punto ha la seguente nota:<emph.end type="italics"/>
			</s>
        </p>
        <p id="N106FC" type="main">
          <s id="N106FE">
				Passano due anni, che mi sono spiegato decisamente su di ciò, rifon-<lb/>
				dendo tutta l’azione ne’ conduttori metallici diversi posti a combaciamento
				<lb/>
				di altro od altri conduttori non metallici, della Classe cioè de’ Conduttori, che
				<lb/>
				ho chiamato <emph type="italics"/>conduttori umidi<emph.end type="italics"/>, perchè o fluidi, o totalmente contenenti qualche
				<lb/>
				umore, fra i quali i corpi animali, e tutte le loro parti fresche e succose.
			</s>
          <s id="N1070E">
				Da quel
				<lb/>
				tempo mi sono sempre più confermato in tal opinione di un’elettricita mossa
				<lb/>
				estrinsecamente: il che ho mostrato in più maniere, ed è pur evidente in mol-<lb/>
				tissimi casi, nella massima parte cioè delle sperienze di questo genere.
			</s>
          <s id="N10716">
				Che se
				<lb/>
				in qualche altro caso, e sperienza può sembrare che gli organi animali, anzi
				<lb/>
				chè i conduttori applicati siano i moventi del fluido elettrico, che in quelli
				<lb/>
				esista veramente una carica o sbilancio di esso fluido, e che questi facciano
				<lb/>
				semplicemente l’officio di scaricatori, se, dico, può sembrare talvolta che i moti
				<lb/>
				muscolari, le convulsioni eccitate procedano da una vera e propria elettricità
				<lb/>
				animale; non dobbiam così facilmente lasciarci sedurre da simili apparenze; e
				<lb/>
				ammettere, così per poco quest’altro principio dell’elettricità propria e attiva
				<lb/>
				degli organi; quando v’è maniera di spiegare anche queste poche sperienze
				<lb/>
				col solo principio che spiega tutte le altre, dell’azione cioè de’ conduttori di-<lb/>
				versi applicati al mutuo combaciamento: principio stabilito già, e dimostrato
				<lb/>
				da me con tante prove.
			</s>
          <s id="N1072E">
				Potendosi spiegare così, non dirò già la maggior parte
				<lb/>
				delle sperienze, ma tutte affatto, l’altro principio o causa supposta diviene su-<lb/>
				perflua; e quindi sommamente improbabile, e tanto più inammissibile, quanto
				<note n="1'" type="editorcomment">
				<p id="N10738" type="main">
					<s id="N1073B">
						<emph type="italics"/>Così nel Manoscritto.<emph.end type="italics"/>
					</s>
				</p>
			</note>
			<lb/>
			che nell’applicazione di tal principio e di qualunque teoria fabbricatavi sopra
			<lb/>
			alle particolari sperienze, incontransi moltissime difficoltà, e anomalie inespli-<lb/>
			cabili, quali certo non s’incontrano nell’applicazione del principio da me stabi-<lb/>
			lito, trovando tutte le sperienze, anche quelle. . . .
			<note n="1'" type="editorcomment">
			<p id="N10752" type="main">
				<s id="N10755">
					<emph type="italics"/>Così nel Manoscritto. <emph.end type="italics"/>
				</s>
			</p>
		</note>
		. . . . . . una facile e chiara
		<lb/>
		spiegazione, come si vedrà.
	</s>
        </p>
        <pb pagenum="303"/>
        <p id="N10764" type="main">
          <s id="N10766">
		[2] <emph type="italics"/>In Br. Ann., T. XI. pag. 85 e Ant. Coll., T. II, P. I, pq. 230, si legge la nota
		<lb/>
		seguente : <emph.end type="italics"/>
	</s>
        </p>
        <p id="N10770" type="main">
          <s id="N10772">
		Non vi è dubbio che il fluido messo in moto in tali sperienze non sia il
		<lb/>
		vero e genuino fluido elettrico, lo stesso cioè che si sbilancia, si accumula, si
		<lb/>
		scarica ec. nelle sperienze dell’elettricità comune; e non SO come si siano imma-<lb/>
		ginato alcuni esser quello un altro fluido, o affatto diverso, o analogo soltanto
		<lb/>
		al fluido elettrico, ma non identico; un fluido animale specifico, d’indole in
		<lb/>
		certo modo elettrica, oppur anche il vero fluido elettrico, ma diversamente
		<lb/>
		modificato, spogliato più o meno delle sue native proprietà e doti, e rivestito
		<lb/>
		di altre, <emph type="italics"/>animalizzato<emph.end type="italics"/> in certo qual modo, cui han dato nome di fluido <emph type="italics"/>elet-<lb/>
		trico-animale. <emph.end type="italics"/>
	</s>
          <s id="N10790">
		Vane idee, precarie e inutili supposizioni! Che serve involger
		<lb/>
		le cose in una nube di termini e di idee vaghe e confuse, da cui in vece di ri-<lb/>
		schiararsi si oscurano vieppiù?
	</s>
          <s id="N10796">
		Riteniamo il fluido elettrico qual è, e attri-<lb/>
		buiamo pure con sicurezza ad esso gli effetti, di cui si tratta.
	</s>
          <s id="N1079A">
		Sì: egli è il fluido
		<lb/>
		elettrico comune e genuino, che messo in corrente per un’azione (mirabile
		<lb/>
		in vero e nuovamente scoperta) de’ conduttori eterogenei applicati a mutuo
		<lb/>
		combaciamento, stimola i nervi, cui invade e attraversa, ed eccita per mezzo
		<lb/>
		di essi le contrazioni de’ muscoli dipendenti; non altrimenti che quando ven-<lb/>
		gono gli stessi nervi percorsi dal fluido elettrico lanciato dai conduttori della
		<lb/>
		macchina ordinaria, da boccie di Leyden cariche, ec..
	</s>
          <s id="N107A8">
		Gli effetti sopra i detti
		<lb/>
		nervi e muscoli sono nell’una e nell’altra maniera similissimi: ed è già questo
		<lb/>
		un grande argomento onde presumere la somiglianza della causa.
	</s>
          <s id="N107AE">
		Osservando
		<lb/>
		poi che. sono gli stessi i coibenti, i buoni, e i cattivi deferenti, tanto dell’elettri-<lb/>
		cità comune, quanto del fluido messo in corrente nelle sperienze in questione,
		<lb/>
		qual dubbio può restar più che sia questo lo stesso stessissimo fluido elettrico?
	</s>
        </p>
        <p id="N107B6" type="main">
          <s id="N107B8">
		Le obbiezioni tratte dal non osservarsi nè scintilla, nè alcun altro de’ con-<lb/>
		sueti segni elettrici, non sono di alcun peso.
	</s>
          <s id="N107BC">
		Questi non si osservano neppure
		<lb/>
		nelle scariche dei conduttori elettrizzati debolissimamente, e delle boccie di
		<lb/>
		Leyden pochissimo caricate, tanto cioè che non arrivano a 1/4 o a 1/10 di grado
		<lb/>
		del più sensibile Elettrometro a boccetta; eppure sono scariche di vero fluido
		<lb/>
		elettrico, che realmente passa e trascorre pe’ conduttori, che da un capo al-<lb/>
		l’altro lo trasmettono; fra i quali se trovinsi compresi i nervi sensibilissimi
		<lb/>
		di un animale, e disposti in guisa, che tutta o gran parte della corrente debba
		<lb/>
		passare ristretta per essi, può questa, ancorchè debole a tal segno, eccitarli
		<lb/>
		sensibilmente, e cagionare il sapore nella lingua, il lampo nell’occhio, e soprat-<lb/>
		tutto le contrazioni nei muscoli dipendenti; come ho mostrato con varie spe-<lb/>
		rienze, applicando appunto l’elettricità artificiale comune.
	</s>
          <s id="N107D2">
		Questa prodigiosa
		<lb/>
		eccitabilità de’ nervi allo stimolo elettrico, specialmente di quegli inservienti
		<lb/>
		a’ moti volontarj, fa che la rana preparata alla maniera di GALVANI ci pre-<lb/>
		senti una specie di <emph type="italics"/>Elettroscopio vivente<emph.end type="italics"/>, che supera di molto in sensibilità; i
		<lb/>
		più fini Elettrometri a fogliette d’oro, ec..
	</s>
          <s id="N107E2">
		Or dunque basta supporre che la
		<lb/>
		<pb pagenum="304"/>
		corrente elettrica, mossa dai semplici combaciamenti de’ conduttori fra loro
		<lb/>
		diversi, è anch’essa molto debole (supposizione naturalissima), debole cioè
		<lb/>
		quanto quella prodotta dall’anzidetta scarica della boccia di Leyden, che ap-<lb/>
		pena può dirsi carica, per intendere come similmente valga soltanto ad ecci-<lb/>
		tare sensazioni e moti muscolari ne’ divisati <emph type="italics"/>Elettroscopj viventi<emph.end type="italics"/> oltremodo
		<lb/>
		sensibili, e non giunga mai a dare nè scintilla, nè altro degli ordinarj segni
		<lb/>
		elettrici.
	</s>
        </p>
        <p id="N107FB" type="main">
          <s id="N107FD">
		[3] <emph type="italics"/>In Br. Ann., T. XI, pag. 90, e in Cart. Volt. L 15 (in due minute successive) tro-<lb/>
		vasi la seguente nota che è un'amplificazione di quella precedentemente riportata da J 32 alla
		<lb/>
		nota<emph.end type="italics"/> [1]:
	</s>
        </p>
        <p id="N10809" type="main">
          <s id="N1080B">
		Da quel tempo mi sono sempre più confermato in tal opinione di un’elet-<lb/>
		tricità propriamente artificiale, voglio dire mossa da causa estrinseca: il che
		<lb/>
		ho mostrato in più maniere, singolarmente colle sperienze del sapore, che ho
		<lb/>
		scoperto eccitarsi sulla lingua coll’artificio de’ metalli; e questo sapore acido
		<lb/>
		od alcalino, secondo che dei due metalli, argento e. g. e zinco, ch’entrano
		<lb/>
		con essa lingua nel circolo conduttore, questo o quello è rivolto contro il di
		<lb/>
		lei apice.
	</s>
          <s id="N10819">
		Ma che più?
	</s>
          <s id="N1081B">
		L’azione de’ conduttori in virtù del semplice loro comba-<lb/>
		ciamento, quando sieno diversi di specie, tal azione che determina una corrente
		<lb/>
		elettrica in giro (seppure il circolo conduttore sia compito), è manifesta, e si
		<lb/>
		tocca con mano nella massima parte delle sperienze, di cui si tratta; in quelle
		<lb/>
		singolarmente in cui il combaciamento coi conduttori umidi, o di 2<emph type="sup"/>a<emph.end type="sup"/> classe si
		<lb/>
		fa alle opposte parti da due metalli, ossia conduttore di 1<emph type="sup"/>a<emph.end type="sup"/> classe, molto diversi
		<lb/>
		uno dall’altro, come argento od oro da una parte, ferro, o meglio piombo o
		<lb/>
		stagno, o assai meglio ancora, zinco dall’altra: nei quali incontri ho io ben anche
		<lb/>
		scoperto qual è la direzione della corrente elettrica da tali combaciamenti ecci-<lb/>
		tata, cioè dallo stagno o zinco per la via del conduttore o conduttori umidi
		<lb/>
		interposti all’oro, o all’argento; e in generale sempre dal metallo superiore al-<lb/>
		l’inferiore attraversando detti conduttori umidi o di 2<emph type="sup"/>a<emph.end type="sup"/> classe; e con forza
		<lb/>
		tanto maggiore, quanto più distano fra loro i due metalli o corpi di 1<emph type="sup"/>a<emph.end type="sup"/> classe;
		<lb/>
		nell’ordine in cui sono posti nella seguente colonna o scala, che dietro a queste
		<lb/>
		sperienze io avea già sbozzata al principio del 1793 (Vegg. le due lettere
		<lb/>
		precedenti e le altre mie Memorie e lettere dirette a diversi, e pubblicate ne’
		<lb/>
		Giornali), e che differisce poco da quell’altra scala o serie, che ci ha data il
		<lb/>
		Dr. PFAFF anch’esso nel 1793, ristretta per allora a pochi metalli, indi più
		<lb/>
		estesa, compresivi cioè varj semimetalli, piriti e miniere, verso la fine del 1794
		<lb/>
		(Vegg. <emph type="italics"/><foreign lang="de">Journal der Physik</foreign><emph.end type="italics"/> di GREN, Vol. VIII, a. 1794).
	</s>
        </p>
      </section>
      <section type="editorcomment">
        <pb pagenum="305"/>
        <p id="N10867" type="head">
          <s id="N10869">
			TAVOLA.
		</s>
        </p>
        <p id="N1086B" type="main">
          <s id="N1086D">
			<emph type="italics"/>De’ conduttori della prima Classe, che posseggono un diverso potere di spingere
			<lb/>
			il fluido elettrico e cacciarlo avanti ne’ conduttori umidi, ossia di seconda
			<lb/>
			Classe.<emph.end type="italics"/>
		</s>
        </p>
        <p id="N10879" type="main">
          <s id="N1087B">
			Zinco.
			<lb/>
			................
			<lb/>
			................
			<lb/>
			................
			<lb/>
			Alcuni di que’ fogli stagnati, che si chiamano impropriamente <emph type="italics"/>carta d’argento<emph.end type="italics"/>.
			<lb/>
			<app><rdg loc="inline">................</rdg><rdg loc="supralinear">................ </rdg></app>Stagnole diverse
			<lb/>
			Piombo.
			<lb/>
			Alcune qualità di Stagno in lastre, o in verghe.
			<lb/>
			Regolo d’Antimonio.
			<lb/>
			Altre qualità di stagno.
			<lb/>
			Alcune qualità di Ferro.
			<lb/>
			Regolo di Bismuto.
			<lb/>
			Altre qualità di Ferro.
			<lb/>
			Bronzi varj.
			<lb/>
			Ottone, Oricalco, ec.
			<lb/>
			Rame.
			<lb/>
			Regolo di Cobalto.
			<lb/>
			Ferro piritoso non cristallizzato.
			<lb/>
			Galena, tessulare, ossia pirite di piombo.
			<lb/>
			Platina.
			<lb/>
			. . . . . . . . . . . . . . . .
			<lb/>
			Mercurio
			<note n="2'" type="editorcomment">
			<p id="N108B9" type="main">
				<s id="N108BC">
					<emph type="italics"/>Nella II Lettera all’Aldini il V. nota essere incorso in errore dovendosi il Mercurio
					<lb/>
					porre vicino al Piombo ed allo Stagno. V. N° XX (B) di questo Volume. <emph.end type="italics"/>
				</s>
			</p>
		</note>
		.
		<lb/>
		Pirite di Ferro cubica.
		<lb/>
		Pirite arsenicale cristallizzata.
		<lb/>
		Oro.
		<lb/>
		Argento.
		<lb/>
		Miniera di Manganese grigia radiata.
		<lb/>
		Rame piritoso.
		<lb/>
		Piombaggine.
		<lb/>
		Alcuni pezzi di Carbone di legna.
	</s>
        </p>
        <pb pagenum="306"/>
        <p id="N108DB" type="main">
          <s id="N108DD">
		Riguardo a questa tavola conviene ch’io faccia osservare due cose.
	</s>
          <s id="N108DF">
		La
		<lb/>
		prima, che le linee punteggiate interposte ad alcuni dei nominati corpi dino-<lb/>tano altrettanti gradi di distanza, ossia di differenza in ordine alla virtù, di
		<lb/>
		cui si tratta.
	</s>
          <s id="N108E7">
		All’incontro dove si succedono immediatamente i corpi specifi-<lb/>
		cati, la differenza è di un grado solamente, ossia picciola; anzi talvolta così
		<lb/>
		picciola, che dalle sperienze da me fatte a questo oggetto mi rimane ancora
		<lb/>
		qualche dubbio, se sian posti tutti giustamente nel luogo, che loro compete,
		<lb/>
		e qualcheduno non debba confondersi affatto, o scambiarsi col vicino: dipen-<lb/>
		dendo fors’anche da circostanze accidentali, che di due collocati immediata-<lb/>
		mente vicini nella tavola, ora il superiore prevalga all’inferiore, or l’inferiore
		<lb/>
		al superiore, secondo che si variano le sperienze.
	</s>
          <s id="N108F7">
		Se però la differenza è poco
		<lb/>
		marcata, talora incerta, e forse anche variabile tra due corpi vicinissimi, ossia
		<lb/>
		distanti di un sol grado nella quì esposta tavola (la quale vorrebbe essere
		<lb/>
		con ulteriori sperienze rettificata ed estesa ancora), ella è marcatissima, nè
		<lb/>
		soggiace ad incertezza od equivoco tra quelli, che distano di molti gradi,
		<lb/>
		come l’argento dal ferro, e questo dai fogli stagnati o dallo zinco; e notabile
		<lb/>
		sì anche, nè punto equivoca, ove la distanza notata dalla Tavola giunga a 3,
		<lb/>
		4 o più gradi, come tra il regolo di Antimonio e quello di Bismuto; tra il Ferro
		<lb/>
		e il Rame; la Platina e l’Argento ec.
	</s>
        </p>
        <p id="N10909" type="main">
          <s id="N1090B">
		La seconda cosa che merita osservazione si è, che non i soli metalli, ma
		<lb/>
		molte miniere, e le piriti singolarmente, ancorchè contengano assai più solfo,
		<lb/>
		il quale è pur materia coibente, che sostanza metallica; riescono non ostante
		<lb/>
		conduttori e motori tanto buoni presso a poco quanto i metalli puri: all’opposto
		<lb/>
		altre miniere ricche, e alcune ricchissime di metallo, ma calciforme, ossia <emph type="italics"/>ossi-<lb/>
		dato<emph.end type="italics"/>, si mostrano assai cattivi conduttori.
	</s>
          <s id="N1091D">
		È osservabile ancora, che le anzi-<lb/>
		dette piriti, o <emph type="italics"/>solfuri metallici<emph.end type="italics"/>, godendo in un colla virtù conduttrice quasi al-<lb/>
		l’istesso grado dei metalli (come dicemmo) anche della facoltà motrice, tengono
		<lb/>
		in ordine a questa dei posti vicini all’argento e all’oro: ai quali pure stanno
		<lb/>
		vicini, cioè uno o due gradi sotto, la piombaggine e il carbone.
	</s>
          <s id="N1092D">
		Tutti questi
		<lb/>
		corpi però io li pongo in una sol classe, che chiamo de' <emph type="italics"/>Conduttori metallici<emph.end type="italics"/>,
		<lb/>
		o 1<emph type="sup"/>a<emph.end type="sup"/> classe.
	</s>
        </p>
        <p id="N1093F" type="main">
          <s id="N10941">
		Or dunque, ritornando al proposito, ogni qualvolta due di tai conduttori
		<lb/>
		e insiem motori di 1<emph type="sup"/>a<emph.end type="sup"/> classe, diversi di specie, combaciando un di quà l’altro
		<lb/>
		di là de’ conduttori umidi o di 2<emph type="sup"/>a<emph.end type="sup"/> classe continui, comunicano anche fra loro, o
		<lb/>
		immediatamente, o per mezzo d’altri anch’essi di 1<emph type="sup"/>a<emph.end type="sup"/> classe, e compiesi così
		<lb/>
		il circolo; ogniqualvolta, dico, han luogo queste condizioni, il fluido elettrico
		<lb/>
		viene smosso e tratto in giro nella direzione, che va da quello di detta 1<emph type="sup"/>a<emph.end type="sup"/> classe,
		<lb/>
		che è superiore nella disegnata tavola, all’altro inferiore, attraversando il
		<lb/>
		conduttore, o conduttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe interposti, rifluendo indi in quel primo,
		<lb/>
		e proseguendo una tal circolazione, finchè non s’interrompe il circolo in alcun
		<lb/>
		luogo: la qual corrente è tanto più forte, quanto i due conduttori di 1<emph type="sup"/>a<emph.end type="sup"/> classe
		<lb/>
		<pb pagenum="307"/>
		sono più diversi, ossia distano più gradi un dall’altro nella tavola o scala sovra-<lb/>
		esposta.
	</s>
          <s id="N10980">
		Tutto ciò ho io dimostrato con tali e tante sperienze, che non lasciano
		<lb/>
		più alcun dubbio.
	</s>
          <s id="N10984">
		Debbe dunque ammettersi che in moltissimi casi ove com-<lb/>
		piesi un circolo o catena di conduttori diversi di specie, anzi in tutti i casi,
		<lb/>
		in cui intervengono nel modo suaccennato due della 1<emph type="sup"/>a<emph.end type="sup"/> classe appunto diversi,
		<lb/>
		eccitasi in virtù de' loro combaciamenti co’ conduttori di 2<emph type="sup"/>a<emph.end type="sup"/> classe interposti,
		<lb/>
		una corrente elettrica; la direzione e la forza della quale viene determinata
		<lb/>
		da quella delle due azioni, che si dispiegano ne' detti respettivi combaciamenti,
		<lb/>
		che prevale.
	</s>
          <s id="N1099E">
		Or se in qualche altro caso e sperienza, in cui o non s’adoprino
		<lb/>
		conduttori metallici, o metalli simili, può sembrare che gli organi animali,
		<lb/>
		anzichè i conduttori applicati, siano i moventi del fluido elettrico; che in quegli
		<lb/>
		esista veramente una carica o sbilancio di esso fluido, e che questi facciano
		<lb/>
		semplicemente l’officio di scaricatori; se, dico, può sembrare talvolta che le
		<lb/>
		convulsioni muscolari procedano da una vera e propria elettricità animale,
		<lb/>
		quale se la figurano i Galvaniani; non dobbiamo così facilmente lasciarci se-<lb/>
		durre da simili apparenze, e ammettere così per poco quest’altro principio
		<lb/>
		dell’elettricità propria ed attiva degli organi, quando vi sia pur maniera di
		<lb/>
		spiegare anche codeste poche sperienze col solo principio, che spiega tutte
		<lb/>
		le altre, dell'azione cioè de’ conduttori diversi applicati a mutuo combacia-<lb/>
		mento: principio già stabilito e dimostrato con tante altre prove.
	</s>
          <s id="N109B6">
		Se pertanto
		<lb/>
		io farò vedere, che possono diffatti spiegarsi così, non che la maggior parte
		<lb/>
		delle sperienze, ma tutte affatto; l’altro principio della supposta elettricità
		<lb/>
		propria e attiva degli organi diverrà superfluo, e quindi sommamente impro-<lb/>
		babile.
	</s>
          <s id="N109C0">
		Dessa poi è tanto più inammissibile, quantochè nell’applicazione di tal
		<lb/>
		principio, e di qualunque teoria fabbricatavi sopra, alle particolari esperienze,
		<lb/>
		incontransi ad ogni passo nuove difficoltà e anomalie inesplicabili, come han
		<lb/>
		dovuto già provare i sostenitori suoi, obbligati ad immaginare ogni sorta di
		<lb/>
		ripieghi, e a moltiplicare ipotesi, per dare una tal quale spiegazione, e conci-<lb/>
		liare in qualche maniera tanti fenomeni disparati e ripugnanti; i quali all’in-<lb/>
		contro non sono più tali, nè presentano anomalie, tostochè si riducano al prin-<lb/>
		cipio da me stabilito, in cui trovano una facile e chiara spiegazione, come si
		<lb/>
		vedrà.
	</s>
        </p>
        <p id="N109D2" type="main">
          <s id="N109D4">
		[4] <emph type="italics"/>In Br. Am., T. XI, pag. 96 e Cart. Volt. L 15 trovasi la seguente nota:<emph.end type="italics"/>
	</s>
        </p>
        <p id="N109DC" type="main">
          <s id="N109DE">
		Così ho avanzato con troppa franchezza nella 2<emph type="sup"/>a<emph.end type="sup"/> delle Lettere scritte l’anno
		<lb/>
		scorso « Che fuori dei metalli, delle miniere, e del carbone di legna, il quale per
		<lb/>
		« la virtù di cui si tratta, non meno che per quella di esser eccellente conduttore,
		<lb/>
		« va posto in compagnia de' metalli, niun’altro conduttore è atto, applicandolo
		<lb/>
		« in qualità di armatura, a produrre nè il sapor elettrico sulla lingua, nè la cor-<lb/>
		« ruscazione nell’occhio, nè il bruciore, nè movimento alcuno ne’ muscoli della
		<lb/>
		« rana la più vivace, e meglio preparata ».
	</s>
          <s id="N109F2">
		Tuttociò va bene, a riserva dell’ul-<lb/>
		<pb pagenum="308"/>
		tima riga, in cui ho oltrepassato il vero dicendo, che non si possano in alcun
		<lb/>
		modo eccitare, senza l’intervento dei conduttori metallici o di 1<emph type="sup"/>a<emph.end type="sup"/> classe, i moti
		<lb/>
		convulsivi de’ muscoli nelle rane comunque vivaci e preparate nella miglior
		<lb/>
		maniera.
	</s>
          <s id="N10A05">
		Ho dunque detto troppo in quello, e in altri passi; come dove torno
		<lb/>
		a dichiarare: « Che nulla mai e poi mai può ottenersi senza di quelli (i condut-<lb/>
		« tori metallici), cioè coi soli deferenti umidi, nelle rane anche più vivaci e
		<lb/>
		« meglio preparate »; e dove replico ancora infine dell’ultima nota « Che non
		<lb/>
		« succedono mai le convulsioni facendo comunicare i nervi della rana CO’ suoi
		<lb/>
		« muscoli mediante arco conduttore, che non sia metallico ».
	</s>
          <s id="N10A11">
		Or si vedrà come
		<lb/>
		debbano tali espressioni correggersi o modificarsi.
	</s>
        </p>
        <p id="N10A15" type="main">
          <s id="N10A17">
		[5] <emph type="italics"/>In Br. Ann., T. XI, pag. 99 trovasi la seguente nota:<emph.end type="italics"/>
	</s>
        </p>
        <p id="N10A1F" type="main">
          <s id="N10A21">
		Nella preparazione della rana alla maniera di GALVANI si pratica comune-<lb/>
		mente di lasciar attaccato ai nervi ischiatici soltanto un pezzetto di spina dor-<lb/>
		sale, cioè tre o quattro vertebre al più: ma io soglio lasciar tutto il tronco
		<lb/>
		colle zampe davanti, recisa unicamente la testa; e ciò mi è di vantaggio e di
		<lb/>
		comodo in molte sperienze.
	</s>
          <s id="N10A2B">
		Truovo del resto spediente di finir di trucidare
		<lb/>
		la rana col passarle uno stecco tutt’al lungo della spinal midolla: con che
		<lb/>
		convellendosi furiosamente, e stendendo ella le gambe posteriori, in pochi
		<lb/>
		istanti e dopo brevi palpitazioni muore affatto; cioè si rilasciano le sue membra
		<lb/>
		e diventano naturalmente immobili, restando solo eccitabili per lungo tempo
		<lb/>
		ancora agli stimoli meccanici, e molto più agli elettrici.
	</s>
          <s id="N10A37">
		In tale stato i moti
		<lb/>
		che vi si destano cogli artifizj dei conduttori ec., non possono essere equivoci,
		<lb/>
		o confondersi con i moti volontarj; come allorchè la rana, per averle conservata
		<lb/>
		illesa la midolla spinale, vive ancora, tuttochè decapitata; o almeno tiene ri-<lb/>
		piegate e attratte le gambe, e fa resistenza a chi gliele stenda, le ritira di nuovo
		<lb/>
		con forza, spesso le vibra calcitrando ec.
	</s>
        </p>
        <p id="N10A43" type="main">
          <s id="N10A45">
		[6] <emph type="italics"/>In Br. Ann., T. XI, pag. 100 trovasi in più: « Modena 1794 ».<emph.end type="italics"/>
	</s>
        </p>
        <p id="N10A4D" type="main">
          <s id="N10A4F">
		[7] <emph type="italics"/>In Br. Ann., T. XI, pag. 101 e in Cart. Volt. L 15 si trova la seguente<emph.end type="italics"/> nota:
	</s>
        </p>
        <p id="N10A57" type="main">
          <s id="N10A59">
		Ecco ciò ch’io scrivea in una lettera all’Ab. TOMMASELLI di Verona in ago-<lb/>
		sto del 1792
		<note n="7'" type="editorcomment">
		<p id="N10A61" type="main">
			<s id="N10A64">
				<emph type="italics"/>Vedi N° VII di questo Volume. <emph.end type="italics"/>
			</s>
		</p>
	</note>
	: « Ho ottenuto molti nuovi fenomeni; tali però, che estendendo
	<lb/>
	« apparentemente gli effetti di siffatta elettricità animale, ne ristringono assai
	<lb/>
	« l’influenza, e distruggono in gran parte le spiegazioni del Dott. GALVANI,
	<lb/>
	« e mostrano qualmente i moti muscolari, che si eccitano coll’artificio delle
	<lb/>
	« armature metalliche, sono d’ordinario effetti d’un’elettricità appunto arti-<lb/>
	« ficiale estrinseca: non sempre però, come si potrebbe essere tentato di cre-<lb/>
	« dere; giacchè ho pur dimostrato,.... che anche per sola forza organica viene
	<lb/>
	« squilibrato e mosso il fluido elettrico tra nervi e muscoli, o tra l’interno e
	<lb/>
	<pb pagenum="309"/>
	« l’esterno di questi; onde sussiste ferma e stabile la grande scoperta di GAL-<lb/>
	« VANI di una vera e propria <emph type="italics"/>elettricità animale<emph.end type="italics"/>, comunque debbasi a più pochi
	<lb/>
	« fenomeni limitare ».
</s>
          <s id="N10A8C">
	E poco dopo: « Ma lasciando le spiegazioni, e conside-<lb/>
	« rando il puro fatto del trasporto di fluido elettrico dall’una all’altra parte
	<lb/>
	« dell’animale occasionato da due armature di diverso metallo applicatevi,
	<lb/>
	« torno a dire, che quando siffatta circostanza è necessaria, cioè che siano ap-<lb/>
	« punto armature diverse, perchè eccitinsi i moti muscolari, di maniera che,
	<lb/>
	« ove siano quelle eguali, questi moti più non succedano; non può dirsi a ra-<lb/>
	« gione che ivi giuochi alcuna vera <emph type="italics"/>elettricità animale<emph.end type="italics"/>, potendosi o dovendosi
	<lb/>
	« quegli effetti attribuire propriamente ad <emph type="italics"/>elettricità artificiale<emph.end type="italics"/>, eccitata di pre-<lb/>
	« sente col nuovo indicato mezzo.
</s>
        </p>
        <p id="N10AAA" type="main">
          <s id="N10AAC">
		« Ma in caso diverso, cioè quando snudato ed isolato il nervo alla maniera
		<lb/>
		« del Dott. GALVANI, si tocca sì questo, che il muscolo in cui s’impianta, con due
		<lb/>
		« capi del medesimo metallo, oppure armati essendo tanto il muscolo, quanto
		<lb/>
		« il nervo coll’istesso metallo, e nella stessa stessissima foggia, si eccitano
		<lb/>
		« nulladimeno le convulsioni; oh! allora sì, che possiamo con sicurezza asserire
		<lb/>
		« esser causa di cotai fenomeni una <emph type="italics"/>vera e propria elettricità animale<emph.end type="italics"/>.
	</s>
          <s id="N10ABE">
		E invero
		<lb/>
		« d’onde mai può venire la mossa al fluido elettrico, non essendovi ragione
		<lb/>
		« per cui venga in virtù delle armature, che sono affatto simili; se non procede
		<lb/>
		« originariamente dalle parti organiche medesime, cui stanno quelle applicate,
		<lb/>
		« in grazia di trovarsi esso fluido sbilanciato tra coteste parti, cioè tra nervo e
		<lb/>
		« muscolo, o tra l’interno e l’esterno del muscolo, in cui penetra e si dirama
		<lb/>
		« esso nervo?
	</s>
          <s id="N10ACC">
		Un tale stato però di naturale elettricità, ossia sbilancio di fluido
		<lb/>
		« negli organi, dura poco dopo la morte dell’animale, e la sua dissezione; e
		<lb/>
		« quindi cessa in pochi minuti di convellersi la rana tentata così: laddove ten-<lb/>
		« tata nell’altra maniera, cioè coll’artificio delle armature dissimili, continua
		<lb/>
		« l’animaletto a sgambettare per ore ed ore, e sì anche applicandole ambedue
		<lb/>
		« all’esterna faccia de’ muscoli, senza snudare alcun nervo ».
	</s>
        </p>
        <p id="N10AD8" type="main">
          <s id="N10ADA">
		Non diversamente mi spiegai in un’altra lunga lettera scritta verso il
		<lb/>
		tempo medesimo ad un celebre Fisico Ollandese il Dott. VAN MARUM, la quale
		<lb/>
		deve essere stata pubblicata negli Atti della Società di Harlem, o in qualche
		<lb/>
		giornale; e nella Memoria mandata in quel torno alla Società R. di Londra,
		<lb/>
		per ordine di cui venne inserita nel Volume delle Transazioni Filosofiche per
		<lb/>
		l’anno 1793.
	</s>
          <s id="N10AE6">
		Trascriverò quì uno squarcio anche di questa. <foreign lang="fr"><quote>Enfin puisqu’avec
		<lb/>
		des armures de differents métaux, appliquées soit aux nerfs seuls, soit aux seuls
		<lb/>
		muscles, on vient à bout d’exciter les contractions dans ceux-ci, et le mou-<lb/>
		vement des membres, on doit conclure que s’il y a des cas (ce qui pourroit
		<lb/>
		bien encore paroître douteux) où la prétendüe decharge entre nerf et muscle
		<lb/>
		est cause des mouvements musculaires dont il s’agit; il y a bien aussi des
		<lb/>
		circonstances, et plus fréquentes, où l’on obtient les mêmes mouvements
		<lb/>
		par un tout autre jeu, une toute autre circulation du fluide électrique.
		</quote></foreign></s>
        </p>
        <pb pagenum="310"/>
        <p id="N10AFB" type="main">
          <foreign lang="fr">
            <s id="N10AFF">
		« Oui: c’est un tout autre jeu de ce fluide (dont on trouble plûtôt l’équi-<lb/>
		« libre que de le retablir) en ce qu’il coule d’une partie à l’autre..... non pas
		<lb/>
		« en conséquence d’un excès ou défaut respectif; mais par une action propre
		<lb/>
		« de ces mêmes métaux, lorsque ceux-ci sont de differente espèce.
	</s>
            <s id="N10B07">
		C’est ainsi que
		<lb/>
		« j’ai découvert une nouvelle loi, qui n’est pas tant une loi d’électricité ani-<lb/>
		« male, qu’une loi d’électricité commune, à laquelle on doit attribuer la plûpart
		<lb/>
		« des phénomenes, qui paroissoient, d’après les expériences de Mr. GALVANI
		<lb/>
		« et plusieurs autres que j’avois faites moi-même à la suite de celles-là, appar-<lb/>
		« tenir à une véritable électricité animale spontanée, et qui n’en sont pas: ce
		<lb/>
		« sont reellément des effets d’une <emph type="italics"/>électricité artificielle<emph.end type="italics"/> très-foible, qui s’excite
		<lb/>
		« d’une manière, dont on ne s’étoit pas douté, savoir par la simple application
		<lb/>
		« de deux armures de differents métaux, comme j’ai indiqué, et j’expliquerai
		<lb/>
		« mieux dans la suite.
	</s>
          </foreign>
        </p>
        <p id="N10B21" type="main">
          <foreign lang="fr">
            <s id="N10B25">
		« Je dois dire ici, qu’à la découverte de cette loi nouvelle, de cette électri-<lb/>
		« cité artificielle jusqu’à présent inconnue, je me défiai d’abord de tout ce qui
		<lb/>
		« m’avoit paru demontrer une électricité animale naturelle dans le sens propre;
		<lb/>
		« et que j’étois sur le point de revenir de cette idée.
	</s>
            <s id="N10B2D">
		Mais, repassant avec un
		<lb/>
		« examen reflechi tous les phénomenes, et repetant les expériences sous ce
		<lb/>
		« nouveau point de vüe, je trouvai enfin que quelques unes soutiennent encore
		<lb/>
		« cet examen, celles par ex. où l’on n’a pas besoin des armures différentes,
		<lb/>
		« ni même d’armure quelconque, un simple fil métallique étant suffisant, ou
		<lb/>
		« tout autre corps qui puisse faire office d’arc conducteur entre le nerf dé-<lb/>
		« pouillé et un des muscles dependants, pour exciter dans ces derniers les con-<lb/>
		« vulsions; et qu’ainsi l’électricité animale naturelle et proprement organique
		<lb/>
		« subsiste, et ne peut pas être renversée entierement.
	</s>
            <s id="N10B3F">
		Les phénomenes qui l’éta-<lb/>
		« blissent, quoique beaucoup plus limités, ne laissent pas que d’être demons-<lb/>
		« tratifs, comme je viens d’indiquer, et je ferai voir plus amplement dans la
		<lb/>
		« suite ».
	</s>
          </foreign>
        </p>
        <p id="N10B47" type="main">
          <s id="N10B49">
		Ma in seguito fui anzi costretto di abbandonare del tutto una tal idea:
		<lb/>
		e come già avea trovato, che nella maggior parte dei casi dovevansi le convul-<lb/>
		sioni eccitate a quella specie di elettricità artificiale, che movono colla lor ap-<lb/>
		plicazione e combaciamento i conduttori dissimili, massime metallici, piut-<lb/>
		tosto che alla supposta elettricità animale; cominciai ben presto a sospettare,
		<lb/>
		che anche negli altri casi assai rari, nelle pochissime sperienze cioè, in cui senza
		<lb/>
		l’intervento de’ metalli diversi succedono pure le convulsioni, e lascian luogo
		<lb/>
		a crederle cagionate da una vera e propria elettricità animale (con che mi com-<lb/>
		piaceva pure di mantener salva, almeno in parte, la teoria di GALVANI), po-<lb/>
		tessero similmente procedere gli effetti da elettricità estrinseca, da una mossa
		<lb/>
		cioè data al fluido mercè l’incontro e combaciamento di conduttori in qualche
		<lb/>
		modo diversi nell’arco di comunicazione: e un tal sospetto andò pur troppo
		<lb/>
		verificandosi, a misura che mi avanzai con più sottili ricerche ed esperienze
		<lb/>
		<pb pagenum="311"/>
		in mille modi variate, a danno della povera elettricità animale, che non ha più
		<lb/>
		onde sostenersi: come in parte ho già fatto vedere ne’ scritti posteriori al 1792,
		<lb/>
		segnatamente nelle altre due Lettere all’Ab. VASSALLI del 1794, e finirò di mo-<lb/>
		strare in questa e nelle seguenti.
	</s>
        </p>
        <p id="N10B6E" type="main">
          <s id="N10B70">
		[8] <emph type="italics"/>In Br. Ann., T. XI, pag. 107 trovasi la seguente nota: « Vegg. la nota 3 », che è quella
		<lb/>
		di cui alla nota<emph.end type="italics"/> [3].
	</s>
        </p>
        <p id="N10B7A" type="main">
          <s id="N10B7C">
		[9] <emph type="italics"/>In Br. Ann., T. XI, pag. 108 trovasi la seguente nota: <emph.end type="italics"/>
	</s>
        </p>
        <p id="N10B84" type="main">
          <s id="N10B86">
		Finchè si leggono soltanto le Memorie di chi sostiene, e di chi nega l’Elet-<lb/>
		tricità Animale in questione; essendo per avventura in maggior numero gli
		<lb/>
		Scritti in favore, massime dopo la pubblicazione delle sperienze, in cui si ecci-<lb/>
		tano le convulsioni nella rana facendo far arco conduttore ad una delle sue
		<lb/>
		gambe senza adoperar metalli, nè altro corpo estraneo all’animale; e mostrando
		<lb/>
		al di più cotesti Scritti una cert’aria di trionfo; è facile restarne preso ed abba-<lb/>
		gliato: tanto maggiormente, che più bella e plausibile, più feconda di applica-<lb/>
		zioni comparendo l’ipotesi di tal elettricità propria degli organi animali, più
		<lb/>
		volentieri si lascia il facile lettore tirare ad essa.
	</s>
          <s id="N10B98">
		A vincere codesta propensione,
		<lb/>
		a toglier d’inganno i prevenuti o sedotti, non basta il racconto e la descrizione
		<lb/>
		anche minuta di altre sperienze in molto maggior numero, che depongono in
		<lb/>
		contrario, quali sono le mie, e che spiegano in tal senso contrario quelle stesse
		<lb/>
		credute favorevoli all’elettricità animale in questione: bisogna per convin-<lb/>
		cerli ch’essi medesimi vedano e tocchino con mano codeste sperienze, che vor-<lb/>
		rebbero non credere se potessero, e che la loro fantasia sfigura quanto può,
		<lb/>
		finchè vengono soltanto narrate.
	</s>
          <s id="N10BA8">
		Ma se avviene così, descrivendole cioè so-<lb/>
		lamente, che si tolga a tali sperienze molto dell’impressione, che dovrebbero
		<lb/>
		fare; succede poi, allorchè son poste sott’occhio, che convincano a dirittura:
		<lb/>
		come è seguito a molti, a cui ho avuto occasione in quest’anno di mostrarle.
	</s>
        </p>
        <p id="N10BB0" type="main">
          <s id="N10BB2">
		[10] <emph type="italics"/>In Br. Ann., T. XI, pag. 110 trovansi in più le parole:<emph.end type="italics"/> « come farò vedere in pro-<lb/>
		gresso » <emph type="italics"/>In Cart. Volt. L 14 trovansi le parole:<emph.end type="italics"/> « come spiegherò in seguito »
	</s>
        </p>
        <p id="N10BC2" type="main">
          <s id="N10BC4">
		[11] <emph type="italics"/>In Br. Ann., T. XI, pag. 113 trovansi le parole:<emph.end type="italics"/> « alle estreme dita e salti all’oc-<lb/>
		chio pel suo colore bianco e di un lucido argenteo o piuttosto di perla ».
	</s>
        </p>
        <p id="N10BCE" type="main">
          <s id="N10BD0">
		[12] <emph type="italics"/>In Br. Ann., T. XI, pag. 121 trovasi l’annotazione:<emph.end type="italics"/> « Vegg. la prima memoria,
		<lb/>
		pag. 77 », cioè: <emph type="italics"/>Seconda memoria, sull’Elettricità animale, N. III<emph.end type="italics"/>, § 43.
	</s>
        </p>
        <p id="N10BE0" type="main">
          <s id="N10BE2">
		[13] <emph type="italics"/>In Br. Ann., T. XI, pag. 122:<emph.end type="italics"/> « Vegg. le mie prime Memorie pubblicate ».
	</s>
        </p>
        <p id="N10BEA" type="main">
          <s id="N10BEC">
		[14] <emph type="italics"/>In Br. Ann., T. XI, pag. 124 trovasi la nota:<emph.end type="italics"/> « Vegg. le prime Memorie ».
	</s>
        </p>
        <p id="N10BF4" type="main">
          <s id="N10BF6">
		[15] <emph type="italics"/>In Br. Ann., T. XI, pag. 124 trovasi la nota:<emph.end type="italics"/> « Vegg. le prime Memorie ».
	</s>
        </p>
        <p id="N10BFE" type="main">
          <s id="N10C00">
		[16]<emph type="italics"/> Qui termina la 3<emph type="sup"/>a<emph.end type="sup"/> lettera stampata in Br. Ann. ed in Ant. Coll.<emph.end type="italics"/>
	</s>
        </p>
      </section>
    </back>
  </text>
</archimedes>
author	Klaus Thoden <kthoden@mpiwg-berlin.mpg.de>
date	Thu, 02 May 2013 11:14:40 +0200
parents	22d6a63640c6
children