1802.J 
nen 
copper. Next to zinc, tinfoil and lead 
appear to be the beft excitors. When the 
bulk of the metals is large, and the quan- 
tity of furface of an animal with which 
they are in contact is confiderable, the 
contractions are both ftronger and more 
readily excited, than when the reverfe of 
this is the cafe. Jf further experiments 
fhould eftablith decidedly, that the mutu- 
al contaét of two different metals is abfo- 
lutely neceflary for the production of Gal- 
vani’s phenomena, may not this circum- 
ftance afford an ufeful teft of the purity 
of the precious metals? Amongft the 
non-conduétors of the Galvanic fluid, the 
author alfo enumerates charcoal, which 
however is #aid to poffefs a conducting 
quality, according to Profeflor Pfaff, if it 
has been well-burned. Oils are fo far 
from conducting, that, if the fingers of 
the perfon holding either the probe or 
the zinc have peripired much, even this 
operates as a complete obftruction to the 
paflage of the influence. When the in- 
teftines of a frog are removed, and its ab- 
domen is filled with oil, no contraétion can 
be excited by placing one metal upon its 
{ciatic nerves, and bringing another in 
conta& with it, either above or below the 
furface of the oil. If the abdomen of a 
frog be filled with mercury, a piece of 
zinc pafled through it, fo as to touch the 
{ciatic nerves, excites contractions; but 
a piece of filver paffed to them excites 
none. Neither are any excited by touch- 
ing the filver; beneath the furface of the 
mercury, with a piece of zinc. Evena 
very thin plate of air obftructs the paflage 
of the Galvanic fluid. The capacity of 
different fubftances, as conductors or non- 
condu&ors, was not affected by differences 
of their temperature. Upon the whole, 
it appears to-be neceflary, that the Gal- 
vanic fluid fhould pafs toa part in a very 
condenfed ftate in order to excite contrac- 
tions. A communication between the 
mu(cles, as well as the nerve and the me- 
tals, is abfolutely requifite, in order that 
contrations may be excited; at leaft a 
communication muft be formed by water. 
If a nerve, carefully dried, is brought 
in contaét with the two metals, mo con- 
tractions can be excited in the mulcles 5 
bot, if it be again moiftened with a few 
drops of water, contractions inftantly take 
place. At the end of this {cétion, the 
author propoles feveral arguments againft 
Calwani’s and Valli s hypothefis concern- 
ing the above phenomena. Should it be 
ever proved, that the phenomena difcover- 
ed by Galvani are effects of the action 
z 
Hifttrical Account of Galvanifin 
42 
of eleétricity, the author cannot think 
Dr. Vall’s hypothefis will be deemed a 
fatisfaétory account of the manner in 
which it produces them. SedfionII. «* Has 
magnetifm any concern in the phenomena 
difcovered by Galvani?’? According to 
the few experiments, which the author had 
an opportunity of making, he anfwers 
this queftion in the negative. Section III. 
‘¢ What are the relations which fubfift be. 
tween the influence difcovered by Galva- 
ni, and the mufcles, the nervous and the 
vafcular fyftems, of animals??? With 
refpect to the mufcles, it appears, that, 
as it feems impoffible to perform a com- 
plete feparation of the mufcular fibres 
from the nerves, a doubt will always arife, 
whether this Galvanic influence operates 
on the mufcles otherwile than through the 
nerves. ‘The author, being not yet ac- 
quainted with the difcoveries of Mangilt, 
made experiments on animals (as he then 
thought) deftitute of nerves, viz. earth- . 
worms and leeches. ‘Thefe, however, as 
the effects of thofe experiments upon 
them had not fo much the appearance of 
involuntary inftantaneous convulfions, as 
of long-continued expreffions of pain and 
difguft, are moft probably endowed with 
a moft exquifite organ of fenfe, and con- 
fequently are not, as has been fuppoled, 
deflitute of a nervous fyftem. The author 
has contributed very interefting facts to 
the inquiry, whether all the nerves of the 
body are equally affected by the Galvanic 
ftimulus, or whether its effeéts are con- 
fined to thofe appropriated to the mufcles 
of voluntary motion. Not difcouraged 
by the ill-fuccefs of his experiments, the 
author fucceeded at laft in making the 
heart, which had already ceafed to beat, 
contract repeatedly by coating its nerves 
with two different metals; but, when a 
a ftick of glafs, wax, or wood, was made 
ufe of inftead of one of the metals, no 
contraction took place. On placing diffe - 
rent metals in the meatus auditorius exter 
nus of both ears, and eftablifhing an infu- 
Jated metallic communication between 
them, the author felt a difagreeable thock 
in hishead. On withdrawing them from 
the ears, he experienced a feeling fimilar 
to that which one has alter emerging trom 
under water. He was not fenfible of 
having hurt his ears by the experiment, 
but, on getting out of bed the next morn- 
ing, he found that an hemorrhage had 
come from one of his ears. On making 
the experiment which occafions the fen- 
fation of a flath ot lightning in the eye, 
he found the flafh much more ftrong in one 
of 
Cr 
