THE HEAT OF THE BODY 487 



Of less importance in man, but of great importance in fur- 

 bearing animals, is the loss of heat through the lungs. In warm 

 weather there is quickened respiration, brought about reflexly 

 through the play of cutaneous sensory impulses of warmth upon 

 the respiratory center. This quickened respiration carries off 

 heat more rapidly both by increasing the amount of air warmed to 

 body temperature in a given time, and by increasing the evapora- 

 tion of water from the lungs. 



Our sensations induce us to add to or diminish the heat in the 

 Body according to circumstances; as by cold or warm baths, and 

 iced or hot drinks. 



As regards temperature regulation by modifying the rate of heat 

 production in the Body, the following points may be noted; on the 

 whole, .such regulation is far less important than that brought 

 about by changes in the rate of loss, since the necessary vital work 

 of the Body always necessitates the continuance of oxidative proc- 

 esses which liberate a tolerably large quantity of heat. The Body 

 cannot therefore be cooled by diminishing such oxidations; nor, on 

 the other hand, can it be safely warmed by largely increasing 

 them. Still, within certain Hmits, the heat production may be 

 controlled in several ways : 



1. Cold increases hunger; and increased ingestion of food in- 

 creases bodily oxidation, as shown by the greater amount of car- 

 bon dioxid excreted in the hours succeeding a meal. This in- 

 crease is probably due to the activity into which the digestive 

 organs and such metabolic organs as the liver arc thrown; hepatic- 

 vein blood is about one degree centigrade (nearly two degrees 

 Fahrenheit) warmer than portal-vein blood, and during digestion 

 much more blood flows through the liver. 



2. Cold inclines us to voluntary exercise; warmth to muscular 

 idleness; and the more the muscles are worked the more heat is 

 produced in the Body. 



3. Cold tends to produce reflex muscular movements, and so in- 

 creased heat production; as chattering of the teeth and shivering. 



4. Certain drugs, as salicylic acid, and perhaps quinine, diminish 

 the heat production of the Body. Their mode of action is ftill 

 obscure. 



On the whole, however, the direct heat-regulating mechanisms 

 of the Human Body itself are not very eHirient, especially as 



