230 THE FLUIDS. 



matters, and 38 grains of mineral substances. An adult man, in a 

 vapor-bath, loses f ounce of sweat in a minute. (Lehm-ann.) 



About 412 cubic inches of carbonic acid gas are excreted from 

 the skin of a full-grown man, in twenty -four hours, and a little less 

 than one-half as much nitrogen. (Abernethy.) 



Origin. It has already been shown (p. 181) that a transudation is 

 constantly occurring upon the surface of the skin, as a mere phy- 

 sical necessity; and doubtless very much of the fluid collectively 

 called the sweat is produced in this way. The precise proportion 

 of the true sweat, however, cannot be ascertained. Certainly, when 

 the amount of perspiration is very suddenly augmented, as in a 

 vapor-bath, it cannot be due to secretion wholly nor principally. 

 But while secretion is probably thus increased, transudation is in- 

 creased to a much greater proportional extent. In cases of colli- 

 quative sweats, and the cold sweat so common in articulo mortis, it 

 is certainly not increased secretion, but mere transudation, which 

 produces the excess of fluid. 



Besides, it is probable that the gases escaping by the skin do so 

 as a mere physical phenomenon, whether termed exhalation or 

 otherwise. 



So far, therefore, as the sweat is actually a secretion, it is doubtless 

 secreted by the epithelial cells lining the tubes forming the per- 

 spiratory glands. But the portion elaborated by them constitutes 

 the insensible rather than the sensible perspiration ; and though it 

 is highly probable that it contains all the substances mentioned as 

 more characteristic of the sweat as lactic, formic, and butyric 

 acids nothing positive is known on this point. 



Uses. One use of the sweat is, doubtless, to regulate the tem- 

 perature of the animal body; an excess of perspiration, and its 

 evaporation, being a cooling process. 



But the main object of the perspiration is the elimination, it is 

 said, of certain deleterious elements from the blood, it being one of 

 the excretions. When we consider that more than 99J- per cent, of 

 the sweat is water (Favre), it hardly appears possible that this ex- 

 creting power of the perspiratory glands has not been overrated. 

 Yet all physicians are aware of the serious consequence resulting 

 from a sudden "check of the perspiration," so called. 



"We doubt not that the perspiratory glands do eliminate excre- 

 mentitious substances, and that their function is therefore important. 

 But it is probable that the gases and volatile substances which 



