ANIMAL HEAT. 273 



it can be carried off by evaporation, collecting upon the skin as a visible 

 moisture, when it is known as the sensible perspiration. The amount 

 discharged during violent exercise has been known to rise as high as 

 380 grammes per hour ; and Southwood Smith* found that laborers 

 in heated gas-works sometimes lost, by both cutaneous and pulmo- 

 nary exhalation, nearly 1600 grammes in the same time. The evapo- 

 ration of this increased quantity of fluid neutralizes the effect of the 

 heated atmosphere, and thus prevents an undue rise of the bodily tem- 

 perature. 



It is possible that certain influences transmitted tkrough the nerves 

 may also have the power of controlling directly the molecular activity 

 of the tissues, and may thus diminish the amount of internal heat at 

 the source of its production ; but the experimental evidence of this 

 action is yet incomplete, and its mode of operation comparatively 

 obscure. 



The production of animal heat, and the regulation of the bodily 

 temperature, by which it is maintained at or near a normal standard, 

 are two of the most important phenomena presented by the living 

 organism. They result from an associated series of vital actions , and 

 are at the same time essential conditions for the continuance of life. 



* Philosophy of Health. London, 1838, chap. xiii. 



