328 PHYSIOLOGICAL CHEMISTRY. 



is 1.99 p. m., has been more exactly determined in later times by 

 ARGUTINSKY. In two steam-bath experiments, in which in the 

 course of -J and f hour he obtained respectively 225 and 330 c. c. 

 sweat, he found 1.61 and 1.24 p. m. urea. In uraemia, and in 

 ischuria in cholera, urea may be secreted in such quantities by the 

 sweat-glands that crystals deposit upon the skin. The mineral 

 bodies consist chiefly of sodium chloride with some potassium 

 chloride, alkali sulphate, and phosphate. The relative amounts of 

 these in perspiration differ materially from the amounts in the 

 urine (FAYEE, KAST). The relationship, according to KAST, is as 

 follows : 



Chlorine : Phosphate : Sulphate 

 In perspiration 1 : 0.0015 : 0.009 



In urine 1 : 0.1320 : 0.397 



KAST found that the proportion of ethereal sulphuric acid to 

 the sulphate sulphuric in sweat was 1 : 12. After the administra- 

 tion of aromatic substances the ethereal sulphuric acid does not 

 increase to the same extent in the sweat as in the urine (see Chap. 

 XIV). 



Sugar may pass into the sweat in diabetes, but the passage of the bile-col- 

 oring matters has not been positively shown in this secretion. Benzoic acid, 

 succinic acid, tartaric acid, iodine, arsenic, mercuric chloride, and quinine pass 

 into the sweat. Uric acid has also been found iii the sweat in gout, and 

 cystin in cystinura. 



Chromhidrosis has been called the secretion of colored sweat. Sometimes 

 sweat has been observed to be colored blue by indigo (Bizio), by pyocyanin 

 (FoRDOs), or by ferro-phpsphate (KOLLMANN). True blood-sweat, in which 

 blood- corpuscles exude from the openings of the glands, has also been ob- 

 served. 



The exchange of gas through the skin in man is of very little 

 importance compared to the exchange of gas by the lungs. The 

 absorption of oxygen by the skin, which was first shown by REG- 

 NAULT and REISET, is very small. The quantity of carbon dioxide 

 eliminated by the skin increases with the rise of temperature 

 (AUBERT, ROHRIG, FuBiia, and RONCHI). It is also greater in 

 light than in darkne'ss. It is greater during digestion than when 

 fasting, and greater after a vegetable than after an animal diet 

 (FuBiia and RotfCHi). According to SCHARLING it is 10 grins., 

 and according to AUBEKT 3.9 grms., in 24 hours. In certain ani- 



