372 HUMAN PHYSIOLOGY 



Two other factors are discovered during muscular 

 activity which are not clearly present during simple 

 exposure to warm air. One of these is deep breathing. 

 It is only certain species of animals which pant when they 

 are warmed from without but all animals breathe deeply 

 when they are producing uncommon quantities of heat 

 internally. The primary service of the increased ventila- 

 tion of the lungs is to provide more oxygen and remove 

 more carbon dioxid but the discharge of heat is promoted 

 at the same time. 



Another means of shaking off heat during exercise is 

 found in the constant shifting of contact between the 

 skin and the air. The effect is that of a breeze. It is 

 plain that a man who is riding a bicycle, running, or 

 walking enjoys this favoring condition. The same is 

 true in a measure of the man who is standing in one spot 

 and swinging his arms; he profits by the fanning of his 

 skin. The air which lies against it at one moment and 

 has become warm and moist is replaced a moment later 

 by cooler and drier air. An important detail is the 

 pumping of air from within the clothing and the sub- 

 stitution of fresh portions. When one is resting, the air 

 in contact with the skin and under the clothing is warm 

 and nearly saturated. Someone has said that "with the 

 exception of head and hands we live in a tropical climate." 



Fever. The body temperature will rise above the 

 standard if heat production is increased without a com- 

 pensating increase in heat loss. It will also rise with a 

 uniform heat production if heat loss is interfered with. 

 The fever of the Cornish miners, to which we have re- 

 ferred, illustrates more particularly the second difficulty. 

 The metabolism was not too high to be offset by thermo- 

 taxis if the external conditions had been reasonable. 

 The combination of high temperature with high humidity 

 led to an accumulation of heat in the tissues. 



It may be said of fever in general that it is not so much 

 the result of high metabolism as of a failure of the 

 mechanisms of heat dissipation. It is true that the 



