86 PHYSIOLOGY CHAP. 



considered retention of heat to be a characteristic of fever, 

 specially noticeable in the period of rigor or shivering. 



Kichet rightly lays stress on the fact that there is an enormous 

 increase in the production of heat during hard muscular work, 

 this increase amounting sometimes to as much as 200 per cent 

 more than the normal. The worker's temperature, however, only 

 rises about a degree or a part of a degree above normal, and 

 quickly returns to its usual level. . This is explained by the fact 

 that the nerve-centres of the worker keep the temperature at the 

 normal point, so that the great increase in the production of heat 

 is counterbalanced by an equivalent loss in the form of external 

 work and of heat by evaporation from the lungs and skin. In 

 the patient with fever, on the contrary, an increase in the pro- 

 duction of heat which never , exceeds 50 per cent causes the 

 temperature to rise to 40-43, because in fever the regulation of 

 temperature by the nerve-centres takes place at an abnormally 

 high level, so that the moderate increase in production is associated 

 with a much smaller increase in the loss of heat. This shows 

 clearly that the essential internal condition causing the rise of 

 temperature during the process of fever is a functional disorder of 

 the nerve-centres on which the regulation of temperature depends. 



All we have learnt in the last two chapters with regard to the 

 exchange of material and energy in man and the higher animals is 

 closely connected with the question so much discussed in times past : 

 whether there exist centres and nerves which are specifically trophic, 

 i.e. the sole function of which is the regulation of the nutrition 

 of the tissues ; and centres and nerves which are specifically 

 thermic, i.e. only for the regulation of thermogenesis. The 

 numerous observations and experiences we have quoted, clearly 

 prove that the nervous system regulates both the nutrition of the 

 tissues and the production of heat. They also show that so far 

 there are no conclusive observations or experiments to prove the 

 existence of centres and nerves of an exclusively trophic or thermic 

 nature. 



I am of the opinion that we may come to the following general 

 conclusion, which I formulated as early as 1889, in my monograph 

 on fasting : 



" The regulation of nutrition and thermogenesis, of the 

 processes of integration and disintegration, or more generally of 

 the exchange of material and energy, whether of each part or of 

 the organism as a whole, is the fundamental function of the 

 nervous system, considered as a whole and a unit, and not of one 

 or other part or segment." 



