Ill, CONFINED IN STAGNANT AIR. II¢ 
appear ; their lethargy augments, even when put 
in the open air; and they generally die. In- 
dependent of being fufficiently clear in itfelf, 
I obtained the moft fatisfa&tory proof that 
thefe convulfions proceed from injured nerves. 
I wounded the mufcles of a frog that had not 
been expofed to confined air, and thefe motions 
which ftimulating ordinarily awakens were ex- 
cited; but they were never convulfive mo- 
tions; On the. other hand, by touching the o- 
rigin of the crural nerves with the inftrument, 
which was an extremely fine needle, the limbs 
fuddenly became convulfed, and then exactly in 
the fame manner as in confined air. When I 
pricked the {pinal marrow or the brain, convul- 
fions were univerfal over the whole body. I have 
never been able to fee either general or partia! 
convulfions by wounding any part of the body 
but the nerves. Thus, from the convulfive 
fpafms in animals confined in clofe veffels, I arm 
induced to fufpect that the pernicious vapour acts 
on the nervous fyftem. 
, Lhad ftill one doubt to felve. I could not re- 
concile the almoft immediate death of frogs, ex- 
pofed to the powerful exhalations of refpiration, 
with the prefervation of life a long time, though 
deprived of the brain. In my work on circula- 
tion, it has been fhewn that frogs will live feveral 
days, though the brain is taken away. But the 
doubt difappeared on feeing their immediate 
Hoe death, 
