INFLUENCE OF NERVOUS SYSTEM. 243 



The influence of external coverings for the body must not 

 be unnoticed. In warm-blooded animals, they are always 

 adapted, among other purposes, to the maintenance of 

 uniform temperature ; and man adapts for himself such as 

 are, for the same purpose, fitted to the various climates to 

 which he is exposed. By their means, and by his command 

 over food and fire, he maintains his temperature on all 

 accessible parts of the surface of the earth. 



The influence of the nervous system in modifying the pro- 

 duction of heat has been already referred to. The experi- 

 ments and observations which best illustrate it are those 

 showing, first, that when the supply of nervous influence 

 to a part is cut off, the temperature of that part falls below 

 its ordinary degree; and, secondly, that when death is 

 caused by severe injury to, or removal of, the nervous 

 centres, the temperature of the body rapidly falls, even 

 though artificial respiration be performed, the circulation 

 maintained, and to all appearance the ordinary chemical 

 changes of the body be completely effected. It has been 

 repeatedly noticed, that after division of the nerves of a 

 limb, its temperature falls ; and this diminution of heat 

 has been remarked still more plainly in limbs deprived of 

 nervous influence by paralysis. For example, Mr. Earle 

 found the temperature of the hand of a paralysed arm to 

 be 70, while the hand of the sound side had a tempera- 

 ture of 92 F. On electrifying the paralysed limb, the 

 temperature rose to 77. In another case, the temperature 

 of the paralysed finger was 56 F., while that of the un- 

 affected hand was 62. 



With equal certainty, though less definitely, the influence 

 of the nervous system on the production of heat, is shown 

 in the rapid and momentary increase of temperature, 

 sometimes general, at other times quite local, which is 

 observed in states of nervous excitement ; in the general 

 Increase of warmth of the body, sometimes amounting to 

 perspiration, which is excited by passions of the mind ; in 



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