THE MAINTENANCE OF THE BODY TEMPERATURE 203 



space, but carrying on his activities in one place for 

 example, in sawing wood his arms and trunk still make 

 short excursions and exchange old air for new. A breeze 

 makes a considerable difference with the heat output of a 

 man's body. 



Fever. When the body temperature is found to rise 

 above its normal level and to persist at an elevation which 

 brings many ill consequences upon the subject, what shall 

 we name as the cause of the disorder? Shall we say that 

 the metabolism is excessive? Studies made upon fever 

 patients show that their nitrogenous metabolism is often 

 surprisingly high, an indication of rapid destruction of the 

 tissues, but the total heat production is not impressively 

 large. We shall more nearly express the facts if we say 

 that there is interference with heat loss. Frequently we 

 can see evidence of a withholding of the perspiration. 

 Perhaps it is best to say that the central fact in fever is the 

 setting up of a false standard by the nervous system to 

 which for a time there is an adherence as strict as that 

 obtaining in health for the normal one. This perverted 

 action of the nervous system is brought about by the 

 poisons in the circulation at such times. Transient fever 

 may be brought on by very severe exercise ; it is experienced 

 by men who run Marathon races. In these cases the con- 

 trolling centers are probably acting in the normal way, but 

 cannot secure the complete removal of the extraordinary 

 quantities of heat which are produced. 



Summary. The maintenance of a nearly uniform body 

 temperature is the result of a balance between heat evolved 

 and heat dissipated. So long as the external conditions 

 are not such as to cause shivering, muscular tension, or 

 instinctive activity of some other form the organism regu- 

 lates its temperature almost wholly by making adjust- 

 ments to promote or to restrict the loss of heat. The 

 wearing of clothing adapted to the season makes it possible 

 to minimize the demands made upon the muscles for extra 

 heat. Decidedly low temperatures and exceptional ex- 

 posure can be withstood only by calling upon the contrac- 

 tile tissues for an increased heat production. 



