796 THE SKIN AND ITS SECRETIONS. 



and LINSER hold that sebum is a mixture of the secretion of the 

 sebaceous glands and of the constituents of the epidermis. HOPPE- 

 SEYLER found, in the sebum, a body similar to casein besides albumin 

 and fat, while ROHMANN and LINSER claim that true fat occurs only to 

 a very slight extent. On saponification the sebum gives an oil, dermolein, 

 which combines readily with iodine, and another body, dermocerin, 

 which melts at 64-65 and which occurs to a considerable extent in 

 dermoid cysts, and which is perhaps identical with the constituent of 

 cysts called cetyl alcohol by v. ZEYNEK. According to AMESEDER this 

 aermocerin is not a pure substance, and the cetyl alcohol obtained from 

 the fat of dermoid cysts is an eicosyl alcohol, C2oH42O, corresponding to 

 arachinic acid. Cholesterin is found in especially large quantities in the 

 vernix caseosa. RUPPEL l found on an average in the vernix caseosa 

 348.52 p. m. water and 138.72 p. m. ether extractives and also mentions 

 the presence of isocholesterin. These claims are disputed by UNNA. 2 

 In his experience isocholesterin does not occur in the vernix fat nor in 

 the sebum of man, although all kinds of sebum contain cholesterin. . 



On account of the opinion generally held that the wax of the plant 

 epidermis serves as protection for the inner parts of the fruit and plant, 

 LIEBREICH 3 has suggested that these combinations of fatty acids with 

 monatomic alcohols are the cause of the waxes having a greater resistance 

 as compared with the glycerin fats. He also considers that the choles- 

 terin fats play the role of a protective fat in the animal kingdom, and he 

 has been able to detect cholesterin fat in human skin and hair, in vernix 

 caseosa, whalebone, tortoise-shell, cow's horn, the feathers and beaks 

 of several birds, the spines of the hedgehog and porcupine, the hoofs of 

 horses, etc. He draws the following conclusion from this, namely, 

 that the cholesterin fats always appear in combination with the keratinous 

 substance, and that the cholesterin fat, like the wax of plants, serves 

 as protection for the skin-surface of animals. Of the sebum fats inves- 

 tigated by UNNA all contained, with the exception of the epidermis fat, 

 besides cholesterin, greater or smaller amounts of cholesterin ester. The 

 epidermis fat, on the contrary, was almost free from esters and consisted 

 chiefly of free cholesterin. 



In the fatty protective substance secreted by the Psylla aim SUNDVIK 4 

 found psylla-alcohol, C 33 H6 8 O, which exists there as an ester in combination with 

 psyllic acid, C 32 H 65 COOH. This alcohol has also been found in the wax of the 

 humble-bee. 



1 Hoppe-Seyler, Physiol. Chem., 760; Linser with Rohmann, Centralbl. f. Physiol., 

 19, 317; see also reference in ibid., 18, from Deutsch. Arch. f. klin. Med., 1904; Riippel, 

 Zeitschr. f. physiol. Chem., 21; Ameseder, ibid., 52. 



2 Monatsch. f. prakt. Dermat., 45. 



3 Virchow's Arch., 121. 



4 Zeitschr. f . physiol. Chem., 17, 25, 32, 53 and 54. 



