398 GENERAL NUTRITION 



human body, the surface being properly protected, is capable of endur- 

 ing for some minutes a heat greater than that of boiling water. Under 

 these conditions the body-temperature is raised but slightly as com- 

 pared with the intense heat of the surrounding atmosphere. In the 

 observations of Dobson, the temperature was raised to 99.5 Fahr. 

 (37.5 C.) in one instance, 101.5 Fahr. (38.6 C.) in another, and 102 

 Fahr. (38.9 C.) in a third, when the body was exposed to a heat of 

 more than 212 Fahr. (100 C.). Delaroche and Berger, however, found 

 that the temperature in the mouth could be increased by 3 to 9 Fahr. 

 (1.65 to 5.05 C.) after sixteen minutes of exposure to intense heat. 

 This was for the external parts only ; and it is not probable that the 

 temperature of the internal organs ever presents such wide variations. 



It is difficult to estimate the temperature in persons exposed to 

 intense cold, as in Arctic explorations, because care is always taken to 

 protect the surface of the body as completely as possible; but experi- 

 ments have shown that the body-heat may be considerably reduced, as 

 a temporary condition, without producing death. In the latter part of 

 the last century, Currie caused the temperature in a man to fall 15 

 Fahr. (8.25 C.) by immersion in a cold bath ; but he could not bring it 

 below 83 Fahr. (28.33 C.). This extreme depression, however, lasted 

 only two or three minutes, and the temperature afterward returned 

 to within a few degrees of the normal standard. The results of experi- 

 ments show that while the normal variations in the temperature in the 

 human subject, even when exposed to great climatic changes, are 

 slight, usually not more than 2 Fahr. (1.1 C.), the body may be 

 exposed for a time to excessive heat or cold, and the extreme limits 

 consistent with the preservation of life may be reached. So far as has 

 been ascertained by direct experiment, these limits are about 83 and 107 

 Fahr. (28.33 and 41.67 C). 



Variations in Different Parts of the Body. The blood becomes 

 slightly lowered in temperature in passing through the general capillary 

 circulation, but the difference is ordinarily not more than a fraction 

 of a degree. This fact is not opposed to the proposition that heat is 

 produced in greatest part in the general capillary system as one of the 

 results of nutritive action ; for the blood circulates with such rapidity 

 that the heat acquired in the capillaries of the internal organs, where 

 little or none is lost, is but slightly diminished before it passes into the 

 arteries, even in circulating through the lungs ; and cutaneous evapora- 

 tion simply moderates the heat acquired in the tissues and keeps it at 

 the proper standard. 



The blood usually is 0.36 to 1.8 Fahr. ( 0.2 to i C.) warmer in the 

 hepatic veins than in the aorta. The temperature in the hepatic veins 



