4 
462° Authentic Experiments éi: the Pheviomena of Galvanifin. f Aprif 
with or without the epidermis, and of the 
different effects of this epidermis, when 
it is wet and when it is dry, appear te 
fuggett to us, that the epidermis is one 
ef thofe fubftances which diminifh or in- 
terrupt the efhcacy of the excitatory arc: 
The epidermis is, as well as the haivs 
and briftles of animal bodies, among the 
number of thofe fubftances which deierve 
the appellation of idio-elec?rtcs. 
g. Examine the fubftances which are 
fit for the formation of the excitatory arc, 
and you will find that the greater part 
of thofe which have been fuccefsfully put 
to this ufe are fubftances capable of aét- 
ing as conductors of the electrical fluid ; 
but that the fubftances which interrupt 
the operation of Galvanifm are generally 
fuch as are well known alfo to refift the 
tran{imiflion of eleétricity. OB Mae 
10. Laftly, it appears, that the Gal- 
/¥anic energy depends, not only upon the 
nature and arrangement ot the component 
parts of the excitatory arc, but on their 
extent too, and on the magnitudes of 
their tranfmitting furfaces. 
III. The committee appear to have 
ufed no lefs care and difcernment in ex- 
periments upon thofe circumitances, which 
though different from the ftructure of the 
Galvanic circle and its two conftituent 
arcs, have, however, a decifive injluence 
upon the exhibition of the phenomena of 
Galvanifit. Some curious obfervations 
were made on the differences in the ftate 
of the parts expofed to the Galvanic action. 
Tt was afcertained, that, frogs trefh from 
the ditches, did by no means exhibit the 
fame phenomena as thofe which had been 
during fome days prelerved in the houte; 
nor did the limbs of animals, when re- 
cently {tripped of the fkin, prefent the 
fame appearances as after they had been 
fubje€ted to avariety of Galvanic experi- 
ments; nor were the fame effects to be 
produced tpon the parts of animal bodies, 
which, after a certain number of trials, had 
been Jett for a while at reft, and then taken 
up again, as upon thotfe which had been 
fubjected to one continued train of experi- 
ments. The committee next examined 
the vqriations in che fuccefs of the expe- 
riments upon a ftrong lively frog, which 
may be produced by varying the mode in 
which the communicator is carried from the 
one fupporter to the other: when the com- 
municater is brought into contaét with 
the fupporter, or is withdrawn from ac- 
tual conta&t with it; when the communi- 
cater is brought flowly, or when it is 
brought rapidly, into contact with the 
fupporter 5, the effests are nearly the fame: 
and a {mart convulfion is, in all thef 
cafes, produced at the moment of the 
commencement of the mutual ¢onta&t, or 
of its ceflation, But, when the frog is 
fatigued, the effeéts are different. Thefe 
fucceflive experiments likewife affeét the 
relults of one another, by means even of 
their fucéeffion folely: And they are alfe 
naturally fubjeét to be influenced by the 
nature of the media, amid which they 
are performed; fuch as common” air; 
water, an eleétrical atmofphere. The 
following are the inferencés which have 
been deduced from this clafs of theie ex- 
periments. 
1. In many cafes tlre Galvanic energy 
is excited by exercife, is exhaufted by 
continued motion, is renovated by reft. — 
2. The multiplicity of the caufes by 
which the experiments of Galvanifm are 
liable to be influenced to fuecefs or fail- 
ure, is fo great, that we cannot, as yet, 
be too cautious in either rejecting or be- 
lieving thefe accounts which we hear, of 
the fuccefs of any fuch experimcnts ; un- 
lefs when we are able accurately to ap- 
preciate all the influencing circumftances. 
3. This is remarkably confirmed by a 
fact, which the committee have related in 
their paper, and which refpeéts the con- 
tinuation of the Galvanic [patin. 
The communicator being fupported by 
the hand, and refting, feemingly, without 
change of pofition, ftill upon the fame 
point of contact, there is known to take 
place a real change in the Galvanic con- 
tact; although the communicator have 
remained thus apparently motionlefs. 
From this, it may be farther inferred, 
that the {malleft poflible change in the re-~ 
lative fituations of the parts of the Gal+ 
vanic circle and the excitatory arc, is ca- 
pable of producing an effect upon the 
fuceptible animal, and of occafioning 
miftakes in regard to the fuccels of the 
experiment, if the utmoft care be not 
taken to notice and eftimate every varia- 
tion that canhappen. | 
4. The truth of the foregoing propo- 
fit‘on is farther confirmed, by the experi- 
ments upon the manner in which the 
Galvanic movements are affected by the 
advancing or the withdrawing of the com- 
municator. For thefe experiments fully 
evince the necefflity for the moft vigilant 
obfervation of every moment in the pro- 
cefs of an experiment, not only collee- 
tively, but in their fucceflion, and at the 
different periods of the operation. 
5. It fhould feem that there are, in the 
formation of the excitatory arc, independ- 
ently of its modes of acting in the Gal- 
vyanic 
