CHAP, v.] NUTRITION. 817 



the brain injury to which, or stimulation of which, produces the 

 effect. While some place it in the median and basal portions of 

 the corpus striatum, others maintain that it is situated in the 

 optic thalamus. The fact however remains that an affection of 

 a very limited portion of the central nervous system may, without 

 producing any other obvious effects, so increase the heat production 

 of the body as to raise the temperature of the body several 

 degrees. 



536. By regulative mechanisms of the kind just discussed 

 the temperature of the warm-blooded animal is maintained within 

 very narrow limits. In ordinary health the temperature of man 

 varies between 36 and 38, the narrower limits being 36*25 and 

 37*5, when the thermometer is placed in the axilla. In the mouth 

 the reading of the thermometer is somewhat ('25 to 1'5) higher; 

 in the rectum it is still higher (about '9) than in the mouth. The 

 temperature of infants and children is slightly higher and much more 

 susceptible of variation than that of adults, and after 40 years of 

 age the average maximum temperature (of health) is somewhat 

 lower than before that epoch. A diurnal variation, independent of 

 food or other circumstances, has been observed, the maximum 

 ranging from 9 A.M. to 6 P.M. and the minimum from 11 P.M. to 

 3 A.M. Meals cause sometimes a slight elevation, sometimes a 

 slight depression, the direction of the influence depending on the 

 nature of the food : alcohol seems always to produce a fall. 

 Exercise and variations of external temperature, within ordinary 

 limits, cause very slight change, on account of the compensating 

 influences which have been discussed above. The rise from even 

 active exercise does not amount to 1 ; when labour is carried 

 to exhaustion a depression of temperature may be observed. In 

 travelling from very cold to very hot regions a variation of less 

 than a degree occurs, and the temperature of inhabitants of the 

 tropics is practically the same as of those dwelling in arctic regions. 



537. Many of the maladies of the body are characterized by 

 an increase of the bodily temperature known as " fever " or 

 "pyrexia," the thermometer very frequently rising to 39" or 40, 

 not unfrequently to 41, and at times reaching 43 or even 44 ; 

 but these higher temperatures cannot long be borne without the 

 organism failing. And as we have said, any increase in man 

 of the bodily temperature beyond 38, or even beyond 37*5, 

 indicates some disturbance. In most cases the rise of temperature 

 has a definite objective cause, some local inflammation or suppura- 

 tion, or, as in specific fevers, the presence in the economy of some 

 "materies morbi," of the nature of an organized germ or of 

 some other nature. We cannot here discuss the connection 

 between the local inflammation or the specific poison and the 

 high temperature, but we have increasing evidence that the 

 high temperature of fever is due, not merely to a diminution of 

 the loss of heat, though this may be a factor, but also, and 



F. 52 



