426 TEMPERATURE AND LIFE. 



ingto the species. Some auimals can live, their temperature being as 

 low as 15° or 20°. Tiie temperature of a rabbit, for example, can fall 

 from 380 or 40o to 20°. That of man may fall to 20°, 25°, and even 24° 

 without resulting in death, according to authentic observations made 

 by Reinke and Nicolayssen upon drunkards. It does not seem, liow- 

 ev^er, according to Claude Bernard, Magendie, and other physiologists, 

 that one can with impunity lower the temperature of warm-blooded 

 animals below 20° 0. At 20° death is almost inevitable; below that 

 point it is certain. The nervous system is destroyed, involving the 

 entire organism. The blood becomes weakened and unequal to per- 

 form its work. 



Surgeons of large armies have left us valuable information concern- 

 ing the effects of intense cold on human beings. In the case of men 

 who are tired and jaded, intense cold is immediately fatal — especially 

 where it is a sudden immersion in very cold water, for in this case the 

 loss of bodily heat is great. Larrey states that in crossing the Beresina, 

 men perished instantly upon entering the water, and Virey and Desgen- 

 ettes testify to similar cases. With some death was caused by cerebral 

 congestion, with others it was caused by anajmia of the brain. When 

 the action of the cold is less sudden, but more prolonged, the result is 

 otherwise. A general benumbing of the body takes place, — of the senses, 

 the brain, the intelligence, a gradual torpor, an invincible sleep from 

 which none awake. " Whoever seats himself, falls into a sleep, and 

 whoever sleeps awakes no more," said Solander. Death is produced by 

 a slow paralysis of the nervous system or by asphyxia. 

 ' Warm-blooded animals are enabled to resist the cold by reason of 

 their very active thermogenesis, which prevents them from becoming 

 chilled. But once let their resistance be overcome and they succumb 

 to much higher temperatures than those which overcome cold-blooded 

 organisms. Many of the latter can endure 10°, 5° and even 0° without 

 perishing. The former die when once their internal temperature falls 

 below 18° or 20°. A more forcible reason why the latter can not resist 

 intense cold is because it destroys the portion congealed and therefore 

 the entire organism. 



Life is also difficult at high temperatures. Man and some animals 

 can, it is true, remain several minutes in a sweating-room in which 

 the temperature is very high — even 100°, 120°, and 130° (Tillet and 

 Duhamel, Delaroche and Berger, etc.) — but under these conditions the 

 stay is always very short ; if prolonged beyond 10 or 15 minutes the 

 experience would prove fatal. The perspiration is so excessive that it 

 produces a loss of the heat which is necessary to counterbalance the 

 temperature to which the atmosphere tends to subject the organism. 

 There is another point to be noticed. Air is a bad conductor, and hot 

 air heats the body incomparably less than water subjected to the influ- 

 ence of heat. Water, on the contrary, is an excellent conductor. It is 

 impossible to endure for any time the contact of water at 50° and 60°. 



