VARIATIONS IN THE HEAT OF THE BODY. 447 



body varies, though within very restricted limits, with extreme changes in 

 climate. The results obtained by Davy, in a large number of observations in 

 temperate and hot climates, show an elevation in the tropics of 0-5 to 3 Fahr. 

 (0-27 to 1*65 C.). It is well known, also, that the human body, the surface 

 being properly protected, is capable of enduring for some minutes a heat 

 greater than that of boiling water. Under these conditions, the animal 

 temperature is raised but slightly, as compared with the intense heat of the 

 surrounding atmosphere. In the observations by 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 tem- 

 perature of the internal organs ever undergoes 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 experiments have shown 

 that the animal 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 tem- 

 perature afterward returned to within a few degrees of the normal standard. 

 The results of experiments show that while the normal variations in the 

 temperature in the human subject, even when exposed to great climatic 

 changes, are very slight, generally not more than two degrees 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. As 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 its temperature in passing through the general capillary circula- 

 tion, but the difference is ordinarily not more than a fraction of a degree. 

 This fact is not opposed to the proposition that animal heat is produced in 

 greatest part in the general capillary system, as one of the results of nutri- 

 tive action ; for the blood circulates with such rapidity that the heat ac- 

 quired in the capillaries of the internal organs, where little or none is lost, 

 is but slightly diminished before the fluid passes into the arteries, even in 

 circulating through the lungs ; and cutaneous evaporation simply moderates 

 the heat acquired in the tissues and keeps it at the proper standard. 



Bernard ascertained that the blood is usually 0-36 to 1-8 Fahr. (O2 to 

 1 C.) warmer in the hepatic veins than in the aorta. The temperature in 

 the hepatic veins is 0-18 to 1-44 Fahr. (0-1 to 0-8 C.) higher than in the 

 portal veins. These results show that the blood coming from the liver is 

 warmer than in any other part of the body. In a series of experiments by 



