398 NUTEITION. 



atmosphere of 13, and there was a diminution of the tem- 

 perature at the diaphragm of 16, and at the pelvis of 18 . 1 

 These results show that while the normal variations in 

 temperature in the human subject, even when exposed to 

 great climatic changes, are very slight, generally not ranging 

 beyond two degrees, 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 

 lias been ascertained by direct experiment, these limits are 

 83 and 107 ; giving a range of about 15 below and 9 

 above the average standard under normal conditions. 2 



Variations in different Parts of the Body. It is to be 

 expected that the temperature of the internal organs should 

 be higher and more constant than that of parts, like the axilla 

 or mouth, more or less exposed to loss of heat by evaporation 

 and contact with the cool air ; and the differences observed 

 in the blood in certain parts, as in the two sides of the heart, 

 have important bearings, as we shall hereafter show, upon 

 the various theories of animal heat. We shall here simply 

 note the variations observed in the blood in different situa- 

 tions, and confine ourselves chiefly to late observations, 

 which have generally been made with apparatus much more 

 reliable and delicate than was formerly employed. 



A great number of experiments have been made upon 

 modifications in temperature accompanying the general 

 change of the blood from arterial to venous ; but perhaps 

 the most exact and elaborate are those by M. Claude Ber- 

 nard. For measuring the temperature in different parts of 

 the vascular system, he used the exceedingly delicate " me- 



1 HUNTER, Observations on certain Parts of the Animal (Economy, London, 

 1792, p. 114. 



2 We have referred only to observations upon the influence of the surround- 

 ing temperature in man and mammals generally. Certain important peculiari- 

 ties in this regard have been observed in hibernating animals, and in reptiles, 

 fishes, and insects, the consideration of which belongs to comparative physi- 

 ology. 



