402 ANIMAL HEAT AND ITS REGULATION 



temperatures provided they do not last too long. The highest authenticated 

 temperatures of patients who afterwards recovered are: 43.6 C., sunstroke; 

 44 C., scarlatina, malaria; 46 C., malaria (?). 



After death the body of course cools down, but not always immediately. 

 Thus it has been shown that the temperature of a body which has died from 

 infectious fevers or injuries to the brain or medulla rises for a time. This is 

 an indication that the metabolism and consequent heat production do not 

 cease everywhere in the body the moment the patient draws his last breath. Also 

 after death from chronic, long-continued diseases, where no such post-mortal 

 rise of temperature is observed, the manner in which the fall of temperature 

 occurs is evidence that combustion in some organs does not cease the moment 

 of death. We find in such cases that the temperature remains unchanged for 

 a time, or falls very slightly, and then declines rapidly. The first stage can 

 only be explained by supposing that heat production is still going on after death 

 (Fig. 149). 



2. THE SOURCE OF ANIMAL HEAT 



The source of animal heat is the combustion going on in the body (cf. 

 page 46). Inasmuch as combustion takes place in all parts of the body, all 

 the different organs participate in the production of heat. And yet the share 

 of the different organs in this process is very different, since in certain organs 

 metabolism is more active than in others. 



The cross-striated muscles are the most important in this connection. They 

 constitute about forty per cent of the total weight of the body, and, if we 

 neglect the skeleton, where the absolute quantity of heat produced is not very 

 significant, they constitute fully fifty per cent of the weight. 



Even the perfectly quiescent muscles generate heat. Meade-Smith deter- 

 mined simultaneously the temperature of the blood in the aorta and in the leg 

 muscles, diverting the blood meantime from the muscles. He was able to show 

 that the temperature of the muscle at the beginning of five-minute periods 

 without blood was as a rule higher, and at the ends of these periods invariably 

 higher than the temperature of the blood in the aorta ; also that the temperature 

 of the muscle always rose during the period. The increase might amount to 

 0.1 C. and the difference between muscle and blood might at the end of the 

 period be 0.6 C. Then with every muscular contraction, as work is performed, 

 additional heat is generated. Indeed the energy consumed as work is never 

 more than a fractional part of that which appears as heat (cf. page 113). 



Next to the muscles, the glands, especially the liver, stomach and intestines, 

 are great producers of heat; but no great importance is to be ascribed to the 

 bones (except the red marrow), the skin or the lungs. Very active metabolism 

 takes place in the gray matter of the central nervous system. But since the 

 metabolism in the -white matter is very slight (cf. Chapter XV), and since 

 the entire nervous system amounts to only about 1.9 per cent of the body 

 weight, it is not to be supposed that this system produces any considerable 

 fraction of the total quantity of heat formed. It is not yet possible to 

 determine more accurately the share of the different organs in this important 

 function. 



