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 Fimke : 4 — 
Relatively to the chlorides, the sulphates and phosphates of sweat are less 
abundant than in urine. The following table is from Kast : 5 — 
Chlorides. 
Phosphates. 
Sulphates. 
Sweat 
Urine 
1 
1 
•0015 
•132 
•009 
•397 
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 6 
found that -363 grm. urea was present in 225 c.c. of sweat collected in 
half an hour, and 440 grm. 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 3T5 per cent, in ammonia; while in the 
other the numbers given are 749 per cent, of total nitrogen in urea, and 
25 T 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 (Julv) . . . 7044 
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 uraemic 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, s 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, 
190. 
1 " Nouveaux elements de phj'siologie humaine," Paris, 1888, 3rd edition, tome ii. p. 
- Loc. cit. 
3 " De Sudore." Diss., Leipzig, 1S51. 
4 Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1858, Bd. iv. S. 36. 
5 Ztsehr. f. physiol. Chan., Strassburg, 1887, Bd. xi. S. 501. ° Loc. cit. 
7 Schottin, loc. cit. 
8 Arch. it«l. debiol.. Turin, 1882, tome ii. ^ Loc. cit. 
