EXCHANGE OF GAS THROUGH THE SKIN. 849 



KAST found that the proportion of ethereal-sulphuric acid to the 

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

 tion of aromatic substances the ethereal-sulphuric acid does not increase 

 to the same extent in the perspiration as in the urine (see Chapter XIV) . 

 The quantity of mineral substances was on an average 7 p. m. 



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

 coloring matters has not been positively shown in this secretion. Benzoic add, 

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

 into the perspiration. Uric acid has also been found in the perspiration in gout 

 and cystine in cystinuria. 



Chromhidrosis is the name given to the secretion of colored perspiration. 

 Sometimes perspiration has been observed to be colored blue by indigo (Bizio), 

 by pyocyanin, or by ferro-phosphate (COLLMANN 1 ). True blood-sweat, in which 

 blood-corpuscles exude from the opening of the glands, has also been observed. 



The exchange of gas through the skin is of great importance for non- 

 scaly amphibians; in mammalia, birds and human beings it is of little 

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

 absorption of oxygen by the skin, which was first shown by REGNATJLT 

 and REISET, is small, and according to ZUELZER amounts under the 

 most favorable circumstances to yiir of the oxygen absorbed by the 

 lungs. The quantity of carbon dioxide eliminated by the skin increases 

 with the rise of temperature (AUBERT, ROHRIG, FUBINI and RONCHI, 

 BARRATT and according to WILLEBRAND beginning at 33 ) 2 . It especially 

 increases with hypersemia of the skin and in particular after muscular 

 activity. It is also greater in light than in darkness. It is greater dur- 

 ing digestion than when fasting, and greater after a vegetable than after 

 an animal diet (FUBINI and RONCHI). The quantity calculated by differ- 

 ent investigators for the entire skin surface in twenty-four hours varies 

 between 2.23 and 32.8 grams. According to SCHIERBECK and WILLE- 

 BRAND 3 the average quantity is 7.5-9 grams, and it is ordinarily given as 

 about 1.5 per cent of the quantity eliminated by the lungs. In a horse, 

 ZUNTZ, with LEHMANN and HAGEMANN,* found for twenty-four hours 

 an elimination of carbon dioxide by the skin and intestine which amounted 

 to nearly 3 per cent of the total respiration. Less than four-fifths of 

 this carbon dioxide came from the skin respiration. The same investi- 

 gators found that the skin respiration equals 2J per cent of the simulta- 

 neous lung respiration. 



1 Bizio, Wien. Sitzungsber., 39; Collmann, cited from v. Gorup-Besanez's Lehrbuch, 

 4. Aufl., 555. 



2 Zuelzer, Zeitschr. f. klin. Med., 53; Aubert, Pfliiger's Arch., 6; Rohrig, Deutsch. 

 Klin., 1872, 209; Fubini and Ronchi, Moleschott's Untersuch. z. Naturlehre, 12; 

 Barratt, Journ. of Physiol., 21; Willebrand, Skand. Arch. f. PhysioL, 13. 



3 See Hoppe-Seyler, Physiol. Chem., 580; Schierbeck, Arch. f. (Anat. u.) Physiol., 

 1892; Willebrand, 1. c. 



4 Arch, f . (Anat. u.) Physiol., 1894, and Maly's Jahresber., 24. 



