PERSPIRATION. 141 



i 



perfectly limpid, colorless, and of a feeble but characteristic 

 odor. Almost all observers have found the reaction of the 

 sweat to be acid ; but it readily becomes alkaline on being 

 subjected to evaporation, showing that it contains some of 

 the volatile acids. In the experiments of Favre it was 

 found that the fluid collected during the first half hour of 

 the observation was acid, during the second half hour it was 

 neutral or feebly alkaline, and during the third half hour, 

 constantly alkaline. The specific gravity of the sweat is 

 from 1003 to 1004. 1 The following is the composition of 

 the fluid collected by Favre : 



Composition of the Sweat. 



Water 995-573 



Urea 0'043 



Fatty matters 0*014 



Alkaline lactates 0*317 



Alkaline sudorates 1-562 



Chloride of sodium, ^ 2-230 



Chloride of potassium, 0'244 



Alkaline sulphates, I soluble in water O012 



Alkaline phosphates, a trace. 



Alkaline albuminates, J 0-005 



Alkaline earthy phosphates (soluble in acidulated water) ... a trace . 

 Epidermic debris (insoluble) a trace. 



1,000-000 



"We have already alluded to the functions of the skin as 

 a respiratory organ and its office in regulating the tempera- 

 ture of the body by evaporation of what is known as the in- 

 sensible perspiration ; but the composition of the sweat in- 

 dicates clearly that the skin is an important organ of excre- 

 tion. Urea is now known to be a constant constituent of 



physiological writers. The subject of the experiment, the surface being first 

 thoroughly cleansed, was enclosed in a metallic case, exposed to an elevated 

 temperature, and the transpiration collected as it flowed, and almost imme- 

 diately analyzed. Each experiment was continued for from an hour to an hour 

 and a half. 



1 ROBIN, Lemons sur les humcurs, Paris, 1867, p. 621. 



