CONTROL OF BODY TEMPERATURE AND FEVER 721 



FEVER 



The clinical application of a Knowledge of the mechanism of heat regu- 

 lation in the animal body concerns the causes of fever. In the most 

 familiar form fever is produced by infectious processes, but it may also 

 be owing to various other causes, among which may be mentioned the 

 parenteral injection of foreign protein, excessive destruction of protein 

 substances in the body itself, the action of certain drugs, and lastly, 

 injury to the base of the brain or lesions of the upper levels of the spinal 

 cord. Various types of fever are recognized: when the temperature re- 

 mains constantly above the normal, it is known as continuous fever; 

 when oscillations occur but the temperature never falls to the normal 

 level, it is known as remittent; when it attains the normal level at cer- 

 tain periods during the day, it is known as intermittent. 



Causes of Fever 



During a sudden rise in temperature -there is, on the one hand, in- 

 creased heat production in the muscles, and on the other, dimin- 

 ished heat loss from the surface of the body. The fever is therefore 

 due to an exaggeration of the processes by which the body normally re- 

 acts to conditions which tend to lower the body temperature. The increased 

 muscular activity thus induced often causes visible contractions, familiar 

 as shivering; and the constriction of the cutaneous blood vessels pro- 

 duces the subjective sensation of chills, and causes the skin to become 

 pale and cold to the touch. The skin muscles also contract, producing 

 "goose skin." During this stage, objective demonstration of the cur- 

 tailment of the skin circulation can be secured by observation of the 

 bloodflow. through the hands and feet (page 283). When the temperature 

 suddenly falls again, the crisis, as it is called, muscles become ' flaccid 

 and produce less heat, and the cutaneous blood vessels dilate, as has 

 been shown by measurements of the bloodflow of the hands and feet. 

 At the same time also, the sweat glands are stimulated and marked per- 

 spiration occurs. 



Concerning the cause of continuous fever, it must be assumed that the 

 balance between heat production and heat loss has been adjusted at a 

 higher plane than normal. We can not explain the fever on the basis 

 either that heat production is permanently increased or that heat loss 

 is permanently diminished, for in neither of these cases would the tem- 

 perature stand at a permanent level but would steadily rise or fall, ac- 

 cording to which mechanism was disturbed. .While set at this higher 

 plane of fever, the thermogenic nerve centers are still capable of re- 

 sponding in the usual way to the influences which cause the body tern- 



