EXCRETIONS 



513 



COMPOSITION OF HUMAN SWEAT 



The total nitrogen content of sweat appears to vary from 0.05 to 0.20 

 per cent, from 50 to 80 per cent being in the form of urea and ammonia. 

 According to the observations of Benedict (a) the average daily loss of 

 nitrogen in the perspiration when the subject performs no muscular work 

 amounts to 0.07 gram, but during hard muscular work as much as 0.2 

 gram may be excreted in a single hour. 



From the data of both Riggs and Plaggemeyer and Marshall the urea 

 * content of sweat appears to amount in round numbers to 0.1 per cent. 

 As the latter workers have pointed out, the relationship between the differ- 

 ent forms of nitrogen in sweat and urine are entirely different. The con- 

 centration of urea in sweat is from three to ten times as high as that of 

 the blood but only one-tenth the concentration in the urine. 



Uric acid occurs in sweat in much smaller amounts than in either blood 

 or urine, the concentration being about, one-twentieth that in blood and 

 one-five-hundredth that in urine. If creatinin is present it exists in very 

 small amounts. 



The greater part of the total solids is made up of sodium chlorid, 

 although according to the observations of Riggs sufficient potassium is 

 gresent to combine with twenty per cent of the chlorin. For example, 

 with a v solid content of 0.5 per cent one might expect a salt content of 

 0.35 per cent. The salt excreted in the sweat may readily amount under 

 certain conditions to two or three grams per day, a quantity ten times 

 that normally present in the feces. Phosphates are present only in traces. 



A diastatic ferment is present in the sweat in appreciable amount. 

 Such dyes as phenolsulphonephthalein are not excreted by the skin nor does 

 the injection of phlorhizin result in the excretion of sugar by the sweat 

 glands. u.n; 



