386 CUTANEOUS SECRETIONS. 



peculiar, more or less, intense odour, which varies with the cutaneous 

 surface from which it has exuded : in most cases it has a weak acid 

 reaction ; indeed it is only sweat which has been collected from the 

 axillae and the feet that is often found to be alkaline. 



It is very difficult to obtain a sufficient quantity of sweat for 

 chemical analysis in order to ascertain its constituents. Thenard 

 and other chemists have employed shirts saturated with sweat; and 

 extracted the sweat from them by various solvents ; but this is the 

 least advisable method, since here there is always a larger or smaller 

 quantity of sebaceous matter mixed with the sweat ; perfectly clean 

 sponges are generally used in this case in order to dry the skin 

 which had been previously cleansed, but is again brought into a 

 state of perspiration. In this way the above mentioned error is 

 certainly much diminished, but it is not altogether avoided ; for we 

 still find in the sweat a very large number of epithelial scales, to which 

 a little of the sebaceous secretion always adheres. The best method 

 is that which was adopted by Anselmino,* who enclosed his arm 

 in a glass cylinder that was rendered as air-tight as possible, and 

 was thus able, in the course of five or six hours, to collect about a 

 tablespoonful of sweat. 



The sweat contains only a very small amount of solid consti- 

 tuents ; Anselmino, whose method of proceeding is certainly the 

 best that has been yet adopted, found that the solid non-volatile 

 constituents varied from 0*5 to 1'25-g-. 



The principal constituent of the sweat, that is to say, the sub- 

 stance which, next to the water, occurs in the largest quantity in 

 this fluid, is, according to the experience of all observers, the 

 chloride of sodium. Phosphate of soda is not found in sweat, and the 

 sulphate only rarely (Simonf), while, on the other hand, the pre- 

 sence of salts of ammonia is very obvious (BerzeliusJ) ; the 

 ammonia in the sweat is not only combined with hydrochloric 

 acid, but also with organic acids; indeed it probably exists as 

 carbonate of ammonia in alkaline sweat. 



Earthy phosphates and a little peroxide of iron are constantly 

 found in the sweat ; they are, however, probably dependent on the 

 admixture of epithelial cells with the fluid under examination ; it 

 is only in consequence of the assumption that lactic acid is con- 

 tained in the sweat, that it has been also assumed that phosphate 

 of lime exists in a state of solution in it. 



* Tiedemaun's Zeitschr. Bd. 2, S. 321 342. 



t Handb. d. med. Ch. Bd. 2, S. 326336 [or English Translation, Vol. 2, 



PP.:IOI-III.] 



J Lehrb. d. Chem. Bd. 9, . 390397. 



