REGULATION OF THE TEMPERATURE. 441 



The mean height of all the temperatures taken during a day in a 

 patient is called the " daily mean " and according to Jaeger it is 37'13 in 

 the rectum in health. A daily mean of more than 37*8 is a " fever 

 temperature," while a mean under 37'0C. is regarded as a " collapse 

 temperature." 



214. Regulation of the Temperature. 



As the bodily temperature of man and similar animals is nearly con- 

 stant, notwithstanding great variations in the temperature of their 

 surroundings, it is clear that some mechanism must exist in the body, 

 whereby the heat-economy is constantly regulated. This may be 

 brought about in two ways ; either by controlling the transformation 

 of potential energy into heat, or by affecting the amount of heat given 

 off according to the amount produced, or to the action of external 



agencies. 



I. Regulatory arrangements governing the production of heat. 



Liebermeister estimates the amount of heat produced by a healthy man 

 at 1'S calories per minute. It is highly probable that, within the body, 

 there exist mechanisms which determine the molecular transformations, 

 upon which the evolution of heat depends (Hoppe-Seyler, Liebermeister). 

 This is accomplished chiefly in a reflex manner. The peripheral ends of 

 cutaneous nerves (by thermal stimulation), or the nerves of the intestine 

 and the digestive glands (by mechanical or chemical stimulation during 

 digestion or inanition) may be stimulated, whereby impressions are 

 conveyed to the heat-centre which sends out impulses through efferent 

 fibres to the depots of potential energy, either to increase or diminish 

 the extent of the transformations occurring in them. The nerve 

 channels herein concerned are entirely unknown. Many considerations, 

 however, go to support such an hypothesis. The following phenomena 

 indicate the existence of mechanisms regulating the production of 

 heat : 



(1.) The temporary application of moderate cold raises the bodily 

 temperature, while heat, similarly applied to the external surface, 

 lowers it (222 and 224). 



(2.) Cooling of the surroundings increases the amount of C0. 7 excreted, 

 by increasing the production of heat (Lieberrneister, Gildermeister), 

 while the consumed is also increased simultaneously; heating the 

 surrounding medium diminishes the CO., (compare Respiration, p. 257). 



D. Finkler found, from experiments upon guinea-pigs, that the production of 

 heat was more than doubled when the surrounding temperature was diminished 

 24C. The metabolism of the guinea-pig is increased in winter 23 per cent, as com- 

 pared with summer, so that the same relation obtains as in the case of a diminution 

 of the surrounding temperature of short duration. 



