PERSPIRATION. 139 



ing upon conditions of temperature and moisture, exercise, 

 the quantity and character of the ingesta, etc. Most of these 

 variations relate to the function of the skin in regulating the 

 temperature of the body ; and it is probable that the elimi- 

 nation of excrementitious matters by the skin is not subject, 

 under normal conditions, to the same modifications, although 

 positive experiments upon this point are wanting. It is not 

 designed, in this connection, to discuss all the experiments 

 that have been made upon the quantity and the modifica- 

 tions of the cutaneous exhalations, and we will only con- 

 sider what appear to be the most reliable of the numerous 

 recorded observations upon this subject. The classical ex- 

 periments of Sanctorius were among the first attempts to 

 determine by the balance the relations of the ingesta to the 

 exhalations ; 1 but these were necessarily imperfect, on ac- 

 count of the difficulty in constructing proper instruments for 

 the investigations, and the cutaneous and pulmonary exhala- 

 tions were estimated together. When there is such a wide 

 range of variation in different individuals and in the same per- 

 son under different conditions of season, climate, etc., it is 

 only possible to give approximate estimates of the quantity 

 of sweat secreted and exhaled in the twenty-four hours ; 

 and more recent observations have shown that the calcula- 

 tions of Seguin and Lavoisier, 9 made in 1Y90, are as nearly 

 correct as possible. These observers estimated the daily 

 quantity of cutaneous transpiration at about two pounds 

 (one pound and fourteen ounces). The estimates of Krause s 

 and of Valentin 4 are a little less, but the difference is not 

 considerable. 



1 SANCTORIUS, Medicina Statica : by JOHN QUINCY, M. D., London, 1723, 

 p. 43, et seq. 



2 SEGUIN ET LAVOISIER, Premier memoiresur la transpiration desanimaux. 

 Histoire de V Academic des Sciences, annee, 1790, Paris, 1797, p. 609. 



3 KRAUSE, Article, Haul. WAGNER'S Handworterbuch der Physiologic, 

 Braunschweig, 1844, Bd. ii., S. 139, et scq. 



4 VALENTIN, Lehrbuch der Physiologie des Menschen, Braunschweig, 1844, 

 Bd. i., S. n 



