RESPIRATORY SYSTEM 213 



3 P-m 37'5 3 C. 



8p.m. . . 37-3 C. 



1 1 p.m. 36*9 C. 



During the night .... 367 C. 

 The effect of muscular exertion is to raise the temperature 



In man by o - 5-ro C. 

 horse ro-r5 C. 



In old age both man and animals show a slight diminution 

 in the average temperature. 



The smaller the animal, the greater is the heat-loss per 

 kilo body-weight and per hour, 1 thus : 



Horse . . i'3 calories per kilo and hour. 

 Adult man . . 1*5 



Dog . 17 



Rabbit . . 5-6 



Porpoise . 7'5 ,, 



Duck . . . 6'O 



Pigeon . .10-0 



Rat . 11-3 



Mouse . . . IQ'O ,, 



Sparrow . 35-0 



Man with his hairless body is compelled to wear clothes in 

 temperate and cold climates in order to prevent heat-loss by 

 radiation. Despite the fact that these garments, as Schuster 

 has shown, conduct heat a hundred times better than the air, 

 still they accomplish their purpose because under the clothes a 

 layer of air is kept more or less at rest in immediate contact 

 with the skin, just as in the fur and feathers of beasts and birds. 

 This adaptation of clothing to the external temperature 

 enables man to live in all climates, provided that the blood- 

 heat does not fall below or rise above certain limits. 



The lowest blood temperature compatible with life for man 

 and mammals is 20 C. if the conditions for breathing are 

 favourable. 



Long exposure to moisture-laden air at 40 C. is fatal in 2-4 

 hours, after which time the body temperature, owing to absence 

 of heat-loss, rises to 4^-46 C. At higher temperatures (49- 



1 Munk-Schultz, loc. cit., p. 322. 



