506 
part of the mufcular fibre, which iffued 
by means of the ftimulus in the nerves. 
from the pofitive electrical part. Dr. 
Eufebius Valli relates, in his Memoig, on 
Animal Electricity, a feries of thirty-two 
experiments, by which he particularly en. 
dGeavours to determine the effects of to- 
bacco and opium on Galvanifm, but he 
found thefe fubftances, as well as other 
poifons, to have no aétion on the electrical 
principle; the gaffes, however, do violent- 
hy affect it. 
Fournal de Phifque, T. XLIL— 
GREN’s Fournal der Phyfk, T. VI. In 
a letter’ of Mr. Bossano CarMina- 
tr to Mr. Galvani, the following no- 
tice is given of the refults of Mr. Vol- 
ta’s experiments :—*‘ Prepared frogs, 
whofe {pinal-marrow, and part of the 
Merves, are coated with metallic plates, 
may be ufed as the moit fenfible ele&tro- 
meters.—The negative and not the pofi- 
tive eleétricity is feated in the nerves.”— 
Mr. Volta defcribes the experiment from 
which he has drawn that conclufion in a 
fetter to Dr. Boronio. . «¢ Not being able 
to trace the nature of this very weak 
eleétricity by means of the moft fenfible 
ele&trometer, I proceeded in another man- 
mer. I called to mind that two phials 
being brought in contaét with each other 
by their fynonymous electric furfaces, do 
not difcharge themfelves, which, however, 
is the cafe as*foon as they touch each 
other with their oppofite electrical points ; 
and I thought it, therefore, not indiffer- 
ent whether I applied the internal coating 
of a weakly charged phial to the mufcle 
er to the nerve. On making a feries of 
experiments according to this,idea, I have 
frequently obferved, that on applying the 
pofitive furface of a phial to the nerve, 535 
or =8,° of the eleétrometer did fuffice tor 
producing contractions in a frog, whereas 
hardly from 2% to 39° were fufficient 
forthe fame purpofe, when the pofitive 
furface of the Leyden phial was brought 
in contact with the mufcle, and the nega- 
tive furface with the nerve. Thence we 
may conclude, that a negative electricity 
is imparted by nature to the nerve, and a 
pofitive electricity to the mufcles.””. Mr. 
Galvani, in reply to this, writes ina let- 
ter addreffed to Mr. Carminati, as fol- 
lows :—‘* Might we not’think it probable 
that, in the cafe where the head of the 
‘Leyden phial was brought in-combination 
with the nerve, the convulfions migh 
ate” 
Inftrudtions by the Abbé Barthelemy to M, Houel. (Jan. 1, 
phia! into the nerve, and thence into the 
internal furface of the mufcular fibre? 
For though, according to my hypothefis, 
a plus of eleétricity exifts in the head of 
the phial as well as in the interior of the 
mufcular fubftance, both electricities are 
moft probably efficient in the fame degree 
of force, and it is moft Ifkely, that the 
weak natural electricity of the nerves is 
overcome by the ftronger efficient electri-. 
city. We may therefore affert, that a 
part of the pofitive electricity of the phial - 
penetrates into the internal fubftance of _ 
the mufcles, by means of the conducting 
fubfiance of the nerves, where, being 
affimilated to their natural electricity, it 
eccafions a difcharge, which is not pro- 
duced by a procefs of the animal machine, 
but. effected by the Leyden phial in the 
hands of the experimentator. : 
(To be Me ) 
—— 
For the Monthly Magazine. * 
INSTRUCTIONS by the celebrated ABBE 
BARTHELEMY, fo M. HOUEL*, fré- 
fpetting bis JOURNEY to NAPLES and 
SICILY. 
N the tour which you, Sir, are about 
I to* undertake through Sicily and 
Greece, you may have frequent opportu- 
nities of colle€ting medals for the King’s 
Cabinet. It is on this account that I beg 
leave to fubjoin fome obfervations, which 
may affift you in making thefe pur- 
chafes. Fata 
I fuppofe you at Naples.—I will pafs 
over in filence the towns of Herculaneum, 
Pompeium, &c. where you will be guided 
by the fuperior knowledge of M. Abbé 
Galiani; M. Hamilton}, whom you will 
alfo meet at Naples, will affift you with 
any correct plans which he may have taken 
of the antiquities of Sicily. i 
If you fhould have a draughtfman with 
you, he might frequently vifit the exca-. 
vations of Pompeium, and either from 
memory, or without being perceived, , 
make fketches of the ftreet, and of fome 
of the buildings which have been difco- 
vered. 
I beg, you will urge the eager expecta- 
* This-artift was at that time painter to 
the King; he publithed at his return, ‘* A’ 
Picturefque Tour in the Iflands of Sicily, 
Malta, and the Lipari, during the Years 
1783, 84, 85, and 87, printed in 4 vols. 
folios The plates are in aquatint, which fades,, 
have entirely, or for the mo& part, been \"very quickly, and greatly fatigues the fight 
owing to the electrical matter baving pe- 
netrated from the internal coating of the 
ee 
when the imprefiigns are half effaced, 
+ Sir William Hamilton, K.B. %. 
tion 
