238 ANIMAL HEAT. 



heat which have the largest respiratory organs and breathe 

 the most air. During sleep, hybernation, and other states 

 of inaction, respiration is slower or suspended, and the 

 temperature is proportionately diminished ; while, on the 

 other hand, when the insect is most active and respiring 

 most voluminously, its amount of temperature is at its 

 maximum, and corresponds with the quantity of respi- 

 ration. Neither the rapidity of the circulation, nor the 

 size of the nervous system, according to Mr. Newport, 

 presents such a constant relation to the evolution of heat. 



On the Regulation of the Temperature of the Human Body. 



The continual production of heat in the body has been 

 already referred to. There is also, of necessity, a continual 

 loss. But in healthy warm-blooded animals, as already 

 remarked, the loss and gain of heat are so nearly balanced 

 one by the other, that under all ordinary circumstances, 

 an uniform temperature, within two or three degrees, is- 

 preserved. 



The loss of heat from the human body takes place chiefly 

 by radiation and conduction from its surface, and by means- 

 of the constant evaporation of water from the same part,, 

 and from the air-passages. In each act of respiration, 

 heat is also lost by so much warmth as the expired air 

 acquires (p. 2IO). All food and drink which enter the 

 body at a lower temperature than itself, abstract a small 

 measure of heat, and the urine and faeces take about a like 

 amount away, when they leave the body. Lastly, some 

 part of the heat of the body is rendered imperceptible, and 

 therefore lost as heat, by being manifested in the form of 

 mechanical motion. 



By far the most important loss of heat from the body, 

 probably So or 90 per cent, of the whole amount, is that 

 which proceeds from radiation, conduction, and evapora- 

 tion from the skin. And it is to this part especially, and 

 in a smaller measure to the air-passages, that we must look 



