CONTROL OF BODY TEMPERATURE AND FEVER 749 



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 tem- 

 perature to change in a normal person. For example, when a fever pa- 

 tient is subjected to a hot bath so that his body temperature rises about 

 0.2 to 0.5 degrees C., sweating occurs just as in a normal individual; or 

 if exercise is taken the increased amount of heat thereby produced in 

 the muscles is dissipated in the usual way. When, on the other hand, 

 the patient is exposed to cold, the vessels of the skin contract and he 

 shivers. 



Although fever is not caused by an actual disturbance of balance be- 

 tween heat production and heat loss, neither of these processes is pro- 

 ceeding at its normal level. That there is a distinct increase in the total 

 heat production of the body in acute fevers in well-developed persons 

 has been shown by means of the respiration calorimeter. This increased 

 heat production is not observed in patients who have been brought into 

 a weakened condition and in whom the muscular tissues have become 

 atrophied by long-continued fever. The increased heat production in 

 continuous fever is mainly dependent upon the increase in body tem- 

 perature and is not one of its causes, as is evident from the fact that far 

 larger quantities of heat are frequently produced in normal individuals 

 as a result of muscular exercise or the taking of large quantities of 

 protein-rich food. The heat thus produced is, however, very quickly 

 dissipated, so that only a temporary rise in temperature occurs, (cf. 

 Hewlett. 57 ) 



Similarly, it can be shown that in continuous fever there is a relative 

 inefficiency in the mechanism of heat dissipation. When the temperature 

 of a normal person is artificially raised through about 1 C., a marked 

 increase in cutaneous bloodflow and profuse perspiration are invariably 

 noted. In a patient with fever of the same degree, on the other hand, 

 there is practically no change in the skin circulation; indeed, it is usually 

 diminished, and there is no unusual perspiration. The heat-regulating 

 mechanism is now fixed on a plane that is higher than the normal, so 

 that although further increase in body temperature, as we have seen, 



