40 SENSIBLE PERSPIRATION. 



What we have considered relates only to the in- 

 sensible perspiration. That which is caused by 

 great heat or severe exercise is evolved in much 

 greater quantity ; and by accumulation at the sur- 

 face, it becomes visible, and forms sweat. In this 

 way, a robust man may lose two or three pounds' 

 weight in the course of one hour's severe exertion ; 

 and if this be suddenly checked, the consequences 

 - : in certain states of the system are often of the most 

 serious description. When the surface of the body 

 is chilled by cold, the blood-vesesls of the skin be- 

 come contracted in their diameter, and hinder the 

 free entrance of the red particles of the blood, which 

 are therefore of necessity collected and retained in 

 greater quantity in the internal organs, where the 

 heat varies very little. The skin consequently be- 

 comes pale, and its papillae contract, forming by 

 their erection what is called the goose's skin. 

 In this state it becomes less fit for its uses ; the 

 sense of touch can no longer nicely discriminate the 

 qualities of bodies, and a cut or bruise may be re- 

 ceived with comparatively little pain. From the op- 

 pression of too much blood, the internal organs, on 

 the other hand, work heavily : the mental faculties 

 are weakened, sleepiness is induced, respiration is 

 oppressed, the circulation languishes, and digestion 

 ceases ; and if the cold be very intense, the vital 

 functions are at last extinguished without pain, and 

 without a struggle. This is a picture of the ex- 

 tremes ; but the same causes which in an aggravated 

 form occasion death produce, when applied in a 

 minor degree, effects equally certain, although not 

 equally marked or speedy in their appearance. 



According to Thenard, the cutaneous exhalation 

 composed of a large quantity of water and a 

 small portion of acetic acid, of muriates of soda and 

 potass, of an earthy phosphate, a little oxide of iron, 

 and some animal matter; but Berzelius considers 

 the acid as lactic, and not the acetic. Some car- 



