dcs Agens Physiques sur la Vie, 



Two cii*cumstance8 are distinguishable, the refrigeration of 

 the body, and the temperature it is capable of sustaining. 

 The cooling is so much less injurious with the young. If 

 two young animals of the same species be cooled down 

 equally'/ the youngest suffers the least. But, in order to 

 lower t6 the same number of degrees the temperature of 

 bodies of different ages, the external heat should be lowered 

 in proportion to the advancemenit of the animal towards 

 maturity, in order to compensate for the difference which the 

 modification of age produces. 



While it is true that the younger animals suffer least from 

 cold, it is, at the same time, to be considered that they cool 

 down more rapidly. On this principle depends the mortality 

 of our domestic fowls and other animals, the management 

 of which requires so much observation and experience in 

 order to rear them. In regions where the temperature is 

 liable to great alterations in the course of the year, man and 

 other vertebrated animals of warm blood are liable to suffer 

 in their health ; for, though cold should produce the resist- 

 ance derived from the necessary constitutional developement 

 of heat, this increase of caloric, having its limits, often ex- 

 poses the constitution to the effects of too great reduction 

 of temperature, as is exemplified in the frozen regions of the 

 North Pole, in Siberia, and in Russia. 



The young of mammiferae, in general, were found by Dr. 

 Edwards to differ very materially in the duration of their 

 lives, in a state of asphyxia, often being limited to from five 

 to eleven minutes, according to their developement at birth, 

 the most advanced in organization living the longest period. 

 The author proved these facts by placing animals in a state 

 of asphyxia under water ; and it is remarkable that, in all 

 his experiments, the voluntary motions were always first 

 destroyed, the involuntary outliving them. With dogs, cats, 

 and rabbits, sensibility existed only three or four minutes. 

 A puppy showed automatic signs of life nearly half an hour. 

 The best divers appear to be able to remain under water 

 from three to four minutes. 



When animals are entirely deprived of aerial contact, it 

 may be inquired, what are the principal functions exercised ? 

 When the air circulates through the lungs, it imparts to 

 the blood a peculiar quality, by which its colour becomes 

 changed. Deprived of this influence from the air, the blood 

 acquires a dark colour, and the nervous function i% simul- 



