420 
POPULAR SCIENCE REVIEW. 
the function of respiration, the living action is put an end to 
for good. 
The statement of this fact will naturally suggest the ques- 
tion, Why is there this difference between warm and cold- 
blooded animals ; between a frog, for instance, and a pigeon ? 
The answer to the question is simple ; the frog requires only, 
for its best life, a comparatively low temperature, and its outer 
covering or skin is a fair conductor of heat. Hence the frog, 
after being entirely frozen, can take up sufficient caloric from a 
warm air to become recharged directly with force throughout 
all its nervous organism ; but the warm-blooded animal, living 
always by the heat it developes in its own body, is protected by 
a skin covered also with a good wow-conducting surface of 
feathers, or fur, or hair: it cannot, therefore, so receive heat 
from without as to be able to recharge its nervous centres from 
any external source of heat ; it dies outright whenever its in- 
ternal and radiating force is cut off. 
To return to our animal made lethargic and insensible by the 
direct abstraction of caloric from the cerebrum. I have said 
that it resembles an animal sleeping after the inhalation of 
chloroform, and this is indeed what is observed. A pigeon will 
lie motionless and insensible for long periods of time, breathing 
slowly, but regularly, and with the heart beating in even time. 
By allowing the temperature to be gradually raised to 60° or 
65° Fahr. there follows steady recovery and return of living 
function ; but the order of recovery is not always the same, 
variations being introduced dependent upon the parts in which re- 
storation begins. Usually, however, when the whole mass of the 
cerebrum, or larger brain, is frozen, recovery of intelligence is 
the first sign exhibited ; then there are attempts at motion, which 
are propulsive forwards, and soon afterwards there is sensation. 
I have, however, seen this order, reversed, the sensation returning- 
before the return of motion. Finally, the animal entirely re- 
covers, and with the recovery memory and all the spell-bound 
faculties return into active play. The brain has been crystallised, 
and it has been loosened back to the fluid state, but it has lost 
as little as it has gained ; all impressions it held it has retained, 
and the light, and the sound, and the touch, and the odour, strike 
again to reach and endow the now impressionable matter. 
Freezing Sections of Brain. 
So far we have seen the effect of removing force from the 
cerebral part of the brain substance as a whole ; let us next 
enquire what is the effect of removing force from special parts 
of the organ. As preliminary to this description I should 
explain, that the brain substance being a bad conductor of 
