818 PYREXIA. [BOOK n. 



indeed chiefly, to an increased production of heat. In fever, the 

 production of carbonic acid, and the consumption of oxygen, that 

 is to say, the metabolic changes of the tissues, are increased. 

 The urea also is increased, and that in such a way as to confirm 

 the view already expressed that much of the heat conies from 

 such a metabolism of the skeletal muscles as, unlike an ordinary 

 contraction, directly involves the nitrogenous elements. The 

 inordinate metabolism of the body at large thus characteristic of 

 fever is shewn by the wasting which it entails. Calorimetric 

 observations also shew in a direct manner that the production of 

 heat is increased. Of course mere increased production alone 

 would be insufficient to raise the temperature of the body, for it 

 might be met, up to a very high limit, by a compensating increase 

 of loss of heat ; but in fever this compensation is wanting, and it 

 is perhaps this absence of due regulation which is most character- 

 istic of the febrile condition. 



In some maladies the bodily temperature falls distinctly below 

 the normal average, reaching for instance 35 or even lower. In 

 such cases there can be little doubt that the condition is due to 

 diminished metabolism and diminished heat production. 



One of the most marked phenomena of starvation is the fall of 

 temperature, which becomes very rapid during the last days of life. 

 The lowered metabolism diminishes the production of heat, and the 

 lowered temperature in turn still further diminishes the meta- 

 bolism. Indeed the low temperature is a powerful factor in bringing 

 about death, for life may be much prolonged by wrapping a starving 

 animal in some bad conductor so as to economise the bodily heat. 



538. Effects of Great Heat. As we said above, the regulative 

 heat mechanism is unable to withstand the strain of too great an 

 external heat or too prolonged an exposure to a great but less 

 degree of heat. The temperature of the body then rises above 

 the normal ; and it has been observed that the temperature is more 

 easily raised by warmth than depressed by cold, at least when 

 neither are very intense. When either in this way by external 

 warmth or through pyrexia the temperature of the body is raised 

 some 6 or 7 above the normal, to 45 or thereabouts, death 

 speedily ensues. The chain of events thus leading to death has 

 not been as yet clearly made out, and most likely the events do not 

 take exactly the same course in all cases ; but we shall probably 

 not go far wrong in attributing death to the fact that the high 

 temperature hurries on the metabolism of the several tissues, of 

 some more than others, at such a spendthrift rate that their capital 

 is soon exhausted. We have seen, eS71, that too warm blood 

 produces dyspnoea, and soon exhausts the metabolic capital of the 

 respiratory centre. Too warm blood similarly hurries on the beats 

 of the heart : an explosion of the contractile substance is each time 

 prematurely brought on before a sufficient quantity of explosive 

 substance is accumulated, each stroke becomes more and more 



