672 SECRETION AND ABSORPTION B Y THE SKIN. 



The specific gravity of human sweat is 1003 to 1006. 



The table on p. 671, from Beaunis, 1 gives the composition of sweat according 

 to Favre, 2 Schottin, 3 and Funke : 4 



Relatively to the chlorides, the sulphates and phosphates of sweat are less 

 abundant than in urine. The following table is from Kast : 5 



There is no doubt that urea is present in the sweat of man; the 

 variations in estimates of the amount by different observers being 

 probably caused by differences in the lapse of time between collection 

 and estimation, and consequent variations in the amount of trans- 

 formation into ammonium carbonate. 



In two lots of sweat collected by the hot-air method, Argutinsky c 

 found that *363 grin, urea was present in 225 c.c. of sweat collected in 

 half an hour, and '410 grin, urea in another sample of 330 c.c, collected 

 in three-quarters of an hour. 



Of the total nitrogen excreted by the skin in one case, 68'5 per 

 cent, was present in urea, and 31 '5 per cent, in ammonia ; while in the 

 other the numbers given are 74'9 per cent, of total nitrogen in urea, and 

 251 per cent, in ammonia. 



The same observer, by taking severe walking exercise in a special 

 suit of clothes, which was extracted at the end of the period of 

 work, and the extract analysed by the Kjeldahl method, obtained results 

 as follows : 



Work. Mgrms. of Nitrogen 



excreted by the Skin. 



20 to 22 kilometres in seven hours (July) . . . 704*4 

 18 to 20 with ascent of 1300 metres (August) . 753 '5 



1600 metres (October) 219-3 



The nitrogen excreted by the skin may amount to 4'7 per cent, 

 of that by the urine, and hence may have to be taken into account in 

 some experiments on nitrogenous metabolism. 



In ursernic conditions, the excretion of urea by the skin is greatly 

 increased, so much so, in some cases, that crystals of urea have been 

 found on the skin. 7 



According to Capranica, 8 creatinine to the extent of '04 per cent, 

 is present in human sweat. The small amounts of fatty acids are made 

 up of formic, acetic, butyric, propionic, and caproic acids. Ethereal 

 sulphates of phenyl and skatoxyl are present in small amount, the 

 proportion of ethereal to inorganic sulphates being, according to Kast, 9 



1 " Nouveaux elements de physiologic hnmaine," Paris, 1888, 3rd edition, tome ii. p. 

 190. 



-Loc. cit. 



3 "De Sudore," Diss., Leipzig, 1851. 



4 Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1858, Bd. iv. S. 36. 



5 Ztschr.f. physiol. Chem., Strassburg, 1887, Bd. xi. S. 501. 6 Loc. cit. 



7 Schottin, loc. cit. 



8 Arch, ital. debiol., Turin, 1882, tome ii. y Loc. cit. 



