[ 21 ] 
perceive any difference, either with regard 
to their intenfenefs or duration. On the 
contrary it appears, that the limb of a frog, 
the nerve of which has not any commu¬ 
nication with the reft of the fyftem, pre- 
ferves its vitality longer than a limb under 
oppofite circumftances. 
Experiment XU. 
I took a live frog, opened its belly to 
difcover the crural nerves, one of which 
I divided, and left the other untouched. 
I then ftripped the fkin off the mufcles 
of both thighs, armed each nerve, and 
with the exciter produced a difcharge, 
fometimes in the one, and fometimes in 
the other limb; The member, the nerve 
of which was divided, gave marks of 
life much longer than the other. This 
effedt, however, is not uniform. 
By repeating this experiment feveral 
times, I had an opportunity of remarking 
fome phenomena, which merit attention. 
C 3 On 
