350 
in still higher temperatures, the pulsations amount- 
ed to 28 or 30 per minute *. From these and simi-* 
lar experiments, Spallanzani concluded that cold di- 
minished the action of the heart and lungs, and, 
when the lethargy was complete, the motion of the 
heart almost entirely ceased, and very little effect 
was then induced on the air f. In like manner, frogs, 
and other animals of this class, became more or less 
lethargic under great reductions of temperature ; 
but the heart continued to beat slowly, and the air, 
in a small degree, was changed ; the consumption of 
oxygen, however, was always proportional to the ele- 
vation of temperature t. These facts prove, that, in 
all the lower animals, the consumption of oxygen 
gas by respiration is preceded by the motion of the 
animal fluids, which again immediately depends on 
the presence and operation of heat. 
658. No experiments, we believe, have yet been 
made on the respiratory process of birds during their 
torpid state ; but if the assertion, that these animals 
often pass the period of hybernation under water, be 
true, they must retain the faculty of reviviscence in 
situations from which air is excluded. As, there* 
fore, in such situations, air is not necessary to their 
existence, it may be reasonably inferred, that when, 
in other situations, the actions of life are suspended, 
the air does not experience any chemical change. 
659. In the mammalia class, we have already ad- 
duced (143.) the example of the marmot as com- 
* Rapports, &c. torn. i. p. 230. f Ibid. p. ?oO. 
J Ibid. p. 470. 
