lil. CONFINED IN STAGNANT AIR. 117 
* Thave fufpected that this poifon may be fatal 
by deftroying the irritability of the mufcles, which 
is poflible in two ways. The mufcular fibre 
may either become too relaxed or too rigid. No 
~fymptom of the mufcles being flaccid appeared, 
when the animals were taken from the confined 
- air, but rather figns of rigidity. Such pheno- 
mena I obferved in frogs: their hind legs and 
thighs were extended ftraight out, as if they had 
been dried. On changing their pofition, or bend- 
‘ing them, refiftance was felt; and their natural 
pofition was refumed when at liberty. The muf- 
éular fubftance feemecd harder to the touch and 
under the knife. However 1 foon difcovered 
that thefe changes in the fibre did not precede 
death, but followed it. If I took frogs dying, or 
juft dead, from the veffel, their limbs were not 
ftretched, and the mufcles preferved fufficient 
‘pliability. On the contrary, extenfion and rigi- 
dity only took place when they remained fome 
time in the veficl. 1 have feen the fame mufcu- 
lar hardnefs and extenfion in the limbs of dead 
frogs continuing immerfed in water. Alteration 
in the mufcular fyftem by no means happens to 
all animals. 
The following fats made me entirely renounce 
the idea of loft irritability. The femoral mufcles 
of a frog difplay great irritability when cut or 
pricked ; they tremble and fuddenly contraé, 
Vor. Il. H | . not 
