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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 pavo,
is according to v. Zeynek * 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
cochenillic acid, CioH8 7 ,
and coccinic acid.
C6H8 0t, the first being the tri-carboxylic acid, and the other the di-carboxylic
acid, of m-cresol. The beautiful purple solution of ammonium carminate has two
absorption-bands between D and E which are similar to those of oxyhemoglobin.
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 Linser claim that true fat occurs only to a very slight
extent. On saponification the sebum gives an oil, dermohin, 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 der-
mocerin is not a pure substance, and the cetyl alcohol, obtained from
the fat of dermoid cysts is an eicosyl alcohol, C20H42O, 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.
’ Pfluger’s Arch., 98.
4
Ber. d. deutsch. chem. Gesellsch., 30.
* Ibid., 42.
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