720 METABOLISM 



so thai when it is required to act, as when the person goes outside to 

 the cold air. it may not do so as promptly as it should, with the result 



■ 



that the body temperature falls somewhat and catarrh, etc., are the 

 result. There can be little doubt that much of the benefit of open-air 

 sleeping is owing to the constant stimulation of the metabolic processes 

 which it causes. 



As will be inferred from what has been said above, the control between 

 heat production and heat loss is effected through a nerve center located 

 in or near the corpora striata. In most animals, when the spinal cord 

 is cut in the cervical region, the body temperature quickly falls unless 

 artifieally maintained. In the case of man, on the other hand, it has 

 usually been observed, after accidental section of the spinal cord in the 

 cervical region, that a rise in temperature occurs. In twent3 T -four un- 

 complicated cases of spinal-cord injury in man, collected from the rec- 

 ords of Guy's Hospital by Gardiner and Pembrey, it was found that 

 nineteen showed hyperthermia (sometimes amounting to 43.9° C.), and 

 • inly five, hypothermia (sometimes 27.6° C.). If the patient lived, the 

 ultimate effect of the section, as in the lower animals, would no doubt 

 be the loss of the power of maintaining a constant temperature. 



The extent to which the animal comes to behave as if cold-blooded after 

 section of the spinal cord varies considerably according to the level of 

 the lesion; if the cord is cut in the upper thoracic region, for example, 

 the regulation against cold, although distinctly less efficient than normal, 

 is far better than when the section is made through the cervical cord. 

 This difference is dependent on the fact that after the loAver lesion much 

 larger muscular groups and skin areas are left intact, so as to make 

 regulation possible. Section of the dorsal cord in mice has been found 

 by Pembrey to abolish entirely the increased metabolism which occurs 

 in normal mice when they are exposed to cold. 



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 tlic body weight (sec page 551). 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 such an accident, the patient is kept 

 nnusuallv warm. 



