1799.] Authentic Experiments oa the Phenamena of Galvanifn. 19% 
ing of tlie epidermis, inthe entire animal 
body, aéts as an obftacle to the decilive 
difplay of the effects of Galvanifm ; and 
that, though from its extreme tenuity, it 
may not altogether prevent thele effects, 
‘yet it cannot but very materially diminifh 
them. 
Il. The ExciraTory ARC is ufually 
formed of three different pieces, made of 
different metals. Of thefe, one muft be 
in contact with the nerve; the other mutt 
touch the mufcle; and the third muft 
form the mean of communication between 
thefe two. This arrangement, though 
not indifpenfibly neceflary, is at lealt the 
qmoft convenient. ‘ 
In refpe& to the ExciraTory Arc, 
the committee examined, 1{t, The ap- 
plication of metallic fubitances to form 
it: in refpect to which they endeavoured 
to afcertain the number and the diverfity 
of the pieces of metal, of which this arc 
may be compofed ; the metallic mixtures 
or alloys which are capable of being em- 
ployed for this ufe; the particular de- 
gree of the friftion of one metal upon 
another, which is favourable to the ex- 
hibition of the phenomena; the different 
fiates, in refpe&t to Galvanifin, of metals 
differently mineralized. adly, The et- 
fedts of the ufe of carbonic fubftances in 
forming the excitatory arc. jdly, The 
effects in the fame formation, of bodies, 
which are either non-conduttors, or elie 
very imperfect conductors of electricity, 
fuch as jet, afphaltus, fulphur, amber, 
fealing-wax, diamond, &c. 4thly, The 
confequences of the interpofition of water, 
and of fubftances moiftened with water, 
between the different parts of the excita- 
tory arc. In forming their excitatory 
arcs toa they made themfelves the chord 
of the arc, they introduced into it animal 
fubftances which had loft their vitality ; 
they-rubbed the fupporters with the dry 
fingers, fo as to mark them with nothing 
but the traces of the perf{piration from the 
fkin. ‘They made, likewife, fome expe- 
fiments for the purpofe of afcertaining 
the relations between, on the one hand, 
the extent and magnitude of the furtaces 
ef the parts compofing the arc, and on 
the other, the effects produced by its 
energy. From their, experiments they 
have alfo drawn fome inierences concern- 
ing the relative efficiencies of the feveral 
conftituent parts of the exciting arc. It 
js impoflible for us here to relate in detail 
all this train of experiments. The fol- 
lowing corollaries exprefs the fubitance of 
thofe general truths, which their authors 
were led to infer from them, 
_ 
x. ‘he excitatory arc poflefles the 
greateft power of Galvanifm, when it is 
compofed of at leaft three diftin® pieces 5 
each of a peculiar nature; the metals, 
water, and humid fubftances, carbo- 
naceous matters, and animal fubftances, 
{tripped of the epidermis, being the only 
materials out of which thele pieces may be 
formed. 
2. Neverthelefs the excitatory arc ap- 
pears to be not deftitute of exciting encr- 
gy» even when it confilts but of one piece 
or of feveral pieces, all of one proper fub- 
fiance. In general it muft be owned, 
identity of nature in the conftituent 
pieces, and particularly in the fupports 
forming the extremities of the arc, di- 
minifhes, in a very fenfible manner, its 
Galvanic energy, 
_ 3. The flighteft difference of nature 
indticed upon the parts, whether by any 
feeble alloy, or by friction with extra- 
neous fubitances, is; at any time, fuffi- 
cient to coimmunicate to the excitatory 
aic, that full power in which the iden- 
tity of its compofition may have made it 
defective. , 
4. f\s the animal are is fulceptible of 
being in part made up of metallic fub> 
ftances, or fuch others as are adapted to 
enter into the compofition of the excita~ 
tory arc; fo, on tne other hand, the ex- 
citatory arc admits of being in pare 
formed of thofe iubftances which are the 
proper components of the animal arc. 
5. The energies of both the excitatory 
and the animal arcs, are alike fulpended 
by the feparation of their component 
parts, or ai leait by the feparation of thele 
parts to a certain diltance. 
6. Even the (mallef degree of mcifture 
is fuliicient to join the parts of the excita- 
tory arc, and to dete.mine their effets 
upon the animal arc. 
7- The influence of the ftate of the at- 
mofphere, and of furrounding circum- 
ftances, upon the fuccefs of the expert- 
ments of Galvanifm, is, confequently, 
very great. In otder therefore to per- 
form thefe experiments with due accuracy, 
‘the ftate of the hygrometer, and of other 
meteorological Initruments, mult be vi- 
gilantly inipested, during their progres ; 
1 . . . S - 
and the influence of the perfons making 
the experiment upon the iphere within 
Which it is made, mutt, likewife, be 
carefully attended t 
8. The experiments which were made 
toaicertain the nature of the animal arc, 
together with thofe made upon the ex- 
cliatory arc, with a view to the compa- 
,? rec 4 ~ . a 
rilon of the cifecis of the flefh of animals, 
with. 

