604 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



When external temperature is excessive and continued, heat-regulation is 

 rendered impossible : if extreme cold, heat-dissipation takes place more rapidly 

 than heat-production, so that bodily temperature falls until death results ; if 

 very hot, heat-dissipation is so interfered with that heat rapidly accumulates 

 within the organism, causing a continuous rise of temperature which finally 

 causes death. 



Abnormal Thermotaxis. By this term is meant the regulation of the heat- 

 processes under conditions in which the mean bodily temperature is maintained 

 at a standard above or below the normal, as in fever and in animals from 

 which the hair has been shaved. It is assumed that under normal conditions 

 the heat-centres are " set/' as it were, for a given temperature of the blood, 

 and that when the temperature of the blood goes above or below this standard 

 a compensatory reaction occurs, so that thermogenesis and thermolysis are 

 properly affected to bring about an adjustment. In fever it may be considered 

 that the centres are set for a higher temperature than the normal ; the higher 

 the fever, the higher the adjustment. The centres may be set for subnormal 

 temperatures, as in the case of a rabbit shaved, whose temperature may remain 

 2 or 3 below the normal for a week or more. When the cause of the ab- 

 normal condition disappears, the centres are readjusted to the normal standard. 



E. POST-MORTEM RISE OP TEMPERATURE. 



A rise of temperature after death is not uncommon ; indeed, in case of 

 violent death of healthy individuals, and after death following convulsions, 

 a rise in temperature is almost invariable. This increase is due to continued 

 heat-production and to diminished heat-dissipation. Heat-production after 

 death may be due to continued chemical activity in the muscles and other 

 structures which are not dead but simply in a moribund state. There is, as it 

 were, a residual metabolic activity which remains in the cells until their tem- 

 perature has been reduced to such a standard that the molecular transforma- 

 tions cease in other words, until the death of the cells occurs. Consequently, 

 the higher the temperature of the individual at the time of somatic death (the 

 cessation of the circulation and respiration), the longer heat-production con- 

 tinues, because the longer the time required to cool the cells to such a degree 

 that their chemical processes no longer go on. Heat is also produced during 

 the development of rigor mortis. The more quickly rigor sets in, and the 

 more intense it is, the greater is the abundance of heat produced. 



The tendency to an increase of bodily temperature is favored by the marked 

 diminution of heat-dissipation which occurs immediately upon the cessation of 

 of the circulation and respiration. Therefore, while both heat-production and 

 heat-dissipation fall at once and enormously at the time of death, heat-dissipa- 

 tion may be decreased to a more marked degiee than heat-production, so that 

 heat may accumulate and the bodily temperature rise. 



Temperature Sense. (See Cutaneous Sensibility, in the section on Special 

 Senses.) 



