THE HEAT OF THE BODY 543 



oxidative processes 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 limits, the heat 

 production may be controlled in several ways: 



1. In cold weather there is an increased appetite for protein 

 foods. The increased consumption of proteins leads, through 

 their specific dynamic action (p. 509) to greater oxidative activity, 

 and so to increased heat production. 



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 still 

 obscure. 



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

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

 protections against excessive cooling. Man needs to supplement 

 them in cold climates by the use of clothing, fuel, and exercise. 



Local Temperatures. Although, by the means above described, 

 a wonderfully uniform bodily temperature is maintained, and by 

 the circulating blood all parts are kept at nearly the same warmth, 

 variations in both respects do occur. The arrangements for equal- 

 ization are not by any means fully efficient. External parts, as the 

 skin, the lungs (which are really external in the sense of being in 

 contact with the air), the mouth, and the nose chambers, are al- 

 ways cooler than internal, and even all parts of the skin have not 

 the same temperature, such hollows as the armpit being warmer 

 than more exposed regions. On the other hand, a secreting gland 

 or a working muscle becomes warmer, for the time, than the rest 

 of the Body, because more heat is liberated in it than is carried off 

 by the blood flowing through. In such organs the venous blood 

 leaving is warmer than the arterial coming to them; while the 

 reverse is the case with parts, like the skin, in which the blood is 

 cooled. An organ colder than the blood is of course warmed by 

 an increase in its circulation, as seen in the local rise of tempera- 

 ture in the skin of the face in blushing. 



