[ 100 ] 
and it is to the inadivity of this prin¬ 
ciple, that in all probability the inftant 
aneous immobility is owing* 
Experiment XCIX. 
The heart when expofed to the contad 
of nitrous air, continues to beat for fome 
time. 
Experiment C. 
Frogs which have their heart expofed, 
do not peri Hi more quickly in nitrous air, 
than others in which it is left under 
natural circumhances. 
I have fometimes feen the movements 
of the heart ceafe, and nofwithftanding 
the animal continue to exercife its volun¬ 
tary motions. This fad: leads me to pre¬ 
fume, that nitrous air ads more upon the 
iirit ibility of the heart and lungs, than 
upon the fentient principle. 
Expert- 
