426 
ef his eyes, which happened to be in a 
ftate of inflammation. He tried, if, 
by infinuating a rod of filver as far as 
poffible up the nofe, he could, by bring- 
ing the filver into contaét with a piece of 
zinc, placed upon his tongue, produce the 
flath in the eye, and the experiment an- 
fwered his moft fanguine expectation. 
During this experiment, the author’s 
friends perceived a very diftinét contrac- 
tion of the iris, when no more light was 
admitted than what was juft fufficient for 
difcerning the pupil, every time the metals 
were brought in contact with each other. 
On repeating this experiment, a friend of 
the author difcovered, that, by placing 
one of the metals as high up as poffible 
between the gums and the upper-lip, and 
the other in a fimilar fituation with re- 
fpe&t to the under-lip, a flafh was pro- 
duced as vivid as that oceafioned by paf- 
fing one of the metals up the nofe, and 
placing the other upon thetongue. Dr. 
Rutherford, to whom this experiment had 
been communicated, remarked, on repeat- 
ing it, that 4 flafh is produced, not only 
at the inftant the metals are brought into 
ecntact, but likewife at the inftant of 
their feparation. What effect the metals 
have on the blood-veffels {eems not to be 
fatisfactorily explained ; the circulation 
of blood, however, appeared to be quick- 
ened feveral times, when the metals, zinc 
and filver, were made to touch each other: 
but the gentlemen, who affifted the author, 
could obferve no change. Sedticn IV. 
‘< An attempt to, inveftigate the fource 
from which the refpective powers of 
nerves and of mufcles are derived.” In 
order to afcertain whether thefe powers 
depend on the brain or on the arteries, 
, the author undertook feveral experiments. 
He divided the {ciatic nerve on one fide, 
and tied the erural artery on the other 
fide. ‘The contraétion occafioned by me- 
talline bodies were, in ail thefe cafes, 
ftronger and of a longer duration in the 
thighs whofe nerves had been divided, 
than in thofe to the arteries of which a 
ligature had been applied. Thus he 
found, that a diminution of the circula- 
tion of any part is accompanied. with a 
proportionable diminution of the refpec- 
tive powers of nerves and mufcles in that 
part. In the experiments with parts that 
were ina ftate of inflammation, he re- 
marked that not only the fenfibility of the 
nerves, but alfo the contractile power of 
the muicle, is increafed, by an increafed 
action of the arteries. ‘* It appears, 
upon the whole (fays the author), tolera- 
Hifterical Account of Galvanifin. 
[Jane [, 
bly certain, that the fanguiferous fyten: 
contributes more immediately than the | 
brain to the fupport of that condition of 
mufcles and nerves, upon which the phe- 
nomena of contraction depend, fince that 
condition is much more injured by inter- 
cepting the influence of the former than 
of the latter.” From fome experiments, 
fuggefted by the opinions of Fontana, it. 
appears, that the conclufion which Fonta- 
na draws from his numerous experiments 
with opium, that the circulation of the 
blood and humours, in the animal ma- 
chine is the vehicle for opium, and that 
without this circulation it would have 
no action on the living body, is the very 
reverfe of that which the author is war- 
ranted to draw from his own experiments 5 
fince the parts moft affected by the aétion 
of opium were not thofe in which the cir- 
culation remained moft entire, but thofe 
in which it had been almoft altogether 
interrupted ; and fince in two parts, where 
the circulation remained equal and entire, 
the action of opium was rendered une- 
qual, by interrupting the communication 
of one of them, by means of the nerves 
of thofe parts to which the opium was 
applied. In an appendix, the author adds 
fome facts, of which we fhall here briefly 
mention thofe that are the moft interelting. 
He frequently difcovered that the irritabi- 
lity of the heart fooner ceafed than the 
contractile power of the mufcles in the 
hind-legs of frogs. He has not found it 
poffible by any quantity either of aqueous 
or of fpirituous folution of opium injected 
upon the brains of frogs, to produce that 
rapid extin&tion of the contraétibility of 
their voluntary mufcles, of which Dr. 
Alexander {peaks. Profeffor Robifon men- 
tions, in a letter to the author, the fol-. 
lowing faéts:—If a piece of zinc is ap- 
plied to the tongue, and is in contact 
with a piece of filver which touches any 
part of the lining of the mouth, noftrils, 
ear, urethra, or anus, the fenfation re- 
fembling tafte is felton the tongue. If 
the experiment be inverted, by applying 
the filver to the tongue, the irritation pro- 
duced by the zinc is not fenfible, except 
in the mouth and the urethra, and is very 
flight. When he applied zinc to a fore 
place, and filver to the tongue, he felt, . 
every time he brought the metals into 
contaét, a very fmart irritation by the 
zincatthe wound. Zinc applied toa hele 
ina tooth, which had fometimes ached a 
little, and filver applied to the infide of 
the cheek, occafion, on bringing the me- 
tals in conta¢t with each other, a very 
{mart 
