AD VANTA GE OF PERSPIRA TJON. 353 



covering, the temperature falls to its normal standard. 

 The explanation is simple. By exposure to cold the 

 radiation of heat from the cutaneous surface is re- 

 duced, the vessels are caused to contract, and the 

 blood driven from instead of towards the surface of 

 the body. Hence, if we want to cool the blood and 

 internal tissues in ordinary fever, we must keep the 

 skin warm and protect it from currents of air. If, 

 however, the temperature is already very high, indeed 

 near the point at which, if reached, death must soon 

 occur, the decided external application of cold is 

 probably the only way of keeping the patient alive 

 (see page 335) ; but we are now discussing the prin- 

 .ciples of treating slight degrees of fever only. By 

 external warmth, then, the blood is determined to 

 the surface, the glands are excited to act, and by 

 free perspiration the blood is relieved of certain 

 constituents which were accumulating in it, to the 

 detriment of the organism. The tension of the vessels 

 of the secreting organs is lessened, and the removal 

 from the blood of water holding in solution various 

 soluble excrementitious substances soon follows. , We 

 all know how pleasant is the sensation produced when 

 moderate perspiration is established in the early stage 

 of a common feverish cold. Even placing the feet 

 in very hot water relieves, in a few minutes, the 

 unpleasant feeling of tension about the head, nostrils, 

 throat, and neck, which, doubtless, we have all expe- 

 rienced. And there is no doubt that in promoting 



