CONTROL OF BODY TEMPERATURE AND FEVER 749 



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

 spiration occurs. It is significant that fever can be caused by injection 

 of very strong sugar solutions intravenously. These attract water from 

 the tissues and so interfere with the giving off of heat. 



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 cannot explain the fever on the basis 

 either that heat production alone is increased or that heat loss alone is 

 diminished, for in neither of these cases would the temperature stand 

 at a permanent level but would steadily rise or fall according to which 

 mechanism was disturbed. The thermogenic nerve centers, while set 

 at the higher plane of fever, are still capable of responding in the usual 

 way to the influences which cause the body temperature to change in a 

 normal person. For example, when a fever patient 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 dissi- 

 pated 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 rate. 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 ) A large heat production also occurs in hyperthyroidism 

 without a corresponding rise in body temperature (page 578). 



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 



