844 THE SKIN AND ITS SECRETIONS. 



thrin MACMUNN found in the shells of crabs and lobsters a blue coloring matter, 

 cyanocrystallin, which turns red with acids and by boiling water. Hcematoporphyrin, 

 according to MACMUNN, also occurs in the integuments of certain of the lower 

 animals. The blue pigment occurring in the fins of the fish, crenilabrus paw, 

 is according to v. ZEYNEK l a chromoprotein. 



In certain butterflies (the pieridinse) the white pigment of the wings consists, 

 as shown by HOPKINS, 2 of uric acid, and the yellow pigment of a uric-acid deriva- 

 tive, lepidotic acid, which yields a purple substance, lepidoporphyrin, on warming 

 with dilute sulphuric acid. The yellow and red pigment of the Vanessa are, 

 according to LINDEN, 3 of an entirely different kind. In this case we are dealing 

 with a compound between protein and a pigment which is allied to bilirubin or 

 urobilin, i.e., a compound similar to haemoglobin. 



In addition to the coloring matters thus far mentioned a few others found in 

 certain animals (though not in the skin) will be spoken of. 



Carminic Acid, or the red pigment of the cochineal, gives on oxidation, accord- 

 ing to LIEBERMANN and VoswiNCKEL, 4 cocheniUic acid, Ci H 8 7 , and coccinic acid. 

 C*H 8 O t , the first being the tri-carboxylic acid, and the other the di-carboxylic 

 acid, of ra-cresol. The beautiful purple solution of ammonium carminate has two 

 absorption-bands between D and E which are similar to those of oxyhaemoglobin. 

 These bands lie nearer to E and closer together and are less sharply defined. Pur- 

 ple is the evaporated residue from the purple-violet secretion, caused by the action 

 of the sunlight, upon the so-called " purple gland " of the mantle of certain species 

 of murex and purpura. According to FRIEDLANDER 5 the pigment is a bromine 

 derivative of indigo and indeed di-bromindigo. 



Among the remaining coloring matters found in invertebrates may be men- 

 tioned blue stentorin, actiniochrom, bonellin, polyperythrin, pentacrinin, antedonin, 

 crustaceorubin, janthinin, and chlorophyll. 



Sebum when freshly secreted is an oily semi-fluid mass which solidifies 

 on the upper surface of the skin, forming a greasy coating. ROHMANN 

 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 LTNSER claim that true fat occurs only ta a very slight 

 extent. On saponification the sebum gives an oil, dermolein, which 

 combines readily with iodine, and another body, dermccerin, 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 der- 

 mocerin 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 



1 Wurm, cited from Maly's Jahresber., 1; Halliburton, Journ. of Physiol., 6; Merej- 

 kowski, Compt. Rend., 93; MacMunn, Proc. Roy. Soc., 1883, and Journ. of Physiol., 7; 

 v. Zeynek, Zeitschr. f. physiol. Chem., 34 and 36, and Wien. Sitz.-Ber. 121, 1912. 



' Phil. Trans., 186. 



3 Pfliiger's Arch., 98. 



4 Ber. d. deutsch. chem. Gesellsch., 30. 



42. 



