TEMPERATURE OF DIFFERENT PARTS OF THE BODY. 407 



a temperature of 37 C., the dog, 39, the cat, 39, the swallow, 

 44 or even higher, are among the warm-blooded, while reptiles 

 and fishes, whose temperature is from 1.7 degrees to 4.5 degrees 

 C. above that of the medium in which they exist, are cold-blooded. 

 The terms warm-blooded and cold-blooded are, however, now not 

 so frequently used as formerly, but in their stead are used the terms 

 homoiothermal and poikilothermal. 



Homoiothermal animals are animals of uniform heat or 

 those whose temperature is unvarying. The thermometer if in- 

 troduced into the rectum of a man, whether he is in the tropics or 

 in the frozen regions of the North, will register about 38 C. The 

 temperature of the surface of his body varies with that of the air 

 a fact with which all are familiar but the internal temperature 

 is the same irrespective of whether it is winter or summer. What 

 is true of man is true also of other mammals and of birds that is, 

 of those animals commonly denominated warm-blooded. 



Poikilothermal animals are animals of varying heat, or those 

 whose temperature varies according to that of the medium air or 

 water in which they live. The frog's temperature is slightly 

 above that of the water, and if this is warm, the temperature in 

 the frog will rise, to fall again when the temperature of the water 

 is lowered. Thus a frog with a temperature of 20.7 C. in water 

 at 20.6 C. will have a temperature of 38 C. when that of the 

 water is raised to 41 C. Fishes, reptiles, amphibia, and insects 

 also exhibit this same variation of temperature, so that cold- 

 blooded and poikilothermal are practically interchangeable terms. 

 A study of insects shows that these creatures produce heat, the 

 thermometer registering, in some experiments on butterflies in 

 active motion, a temperature of 5 degrees C. above that of the air. 

 These insects are poikilothermal. The same power of generating 

 heat is observed also in plants. The amount of heat varies under 

 different circumstances, being especially marked at the time of 

 germination and flowering, sometimes from 5 degrees to 10 degrees 

 C. above that of the air. 



Temperatures of Different Animals. The following 

 table gives the temperatures of some of the more common animals : 



Mammals. 



Centigrade. 



Sheep . . 37.3-40.5 

 Ape . . 35.5-39.7 

 Dog . . . 37.4-39.6 

 Horse . . 36.8-37.5 

 Ox . 37.5 



Birds. 



Centigrade. 



Duck . . . 42.5-43.9 

 Turkey . . 42.7 

 Chicken . 43.0 



Poikilothermal animals. 



Temperature above 

 surrounding medium. 



Frog . . 0.32- 2.44 degrees C. 

 Snakes . 2.50-12.0 degrees C. 

 Fish . . 0.50- 3.0 degrees C. 



Temperature of Different Parts of the Human Body. 



The temperature of the skin at the middle of the upper arm is 

 35.4 C., while in the sole of the foot it is but 32.26 C. In the 



