748 METABOLISM 



In the light of these experiments it is probable that the difference in 

 the effects produced on body temperature by section of the cervical 

 spinal cord in man and the lower animals depends on the relative im- 

 portance of the heat-producing and heat-dissipating mechanisms. When 

 the control of heat loss is paralyzed in the smaller animals, the cooling 

 of the body becomes excessive in relation to the amount of heat produced 

 in the paralyzed muscles, because the body surface is extensive in com- 

 parison with the body weight (see page 586). In the larger animals such 

 as man, on the other hand, the cooling effect is much less marked, espe- 

 cially when, as is common after spinal cord injuries, the patient is kept 

 unusually warm. 



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. 



The Mechanism of Fever 



During a sudden rise in body 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 tone 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 296). When the temperature 

 suddenly falls again, (the crisis, as it is called) the 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. 



