MELANINE. 97 



the urine, both of which contain slight traces of its presence. It is also 

 contained in the hair, where it forms sometimes as much as 7 per cent, 

 of the incombustible ingredients. It is supplied to the body in ample 

 abundance by ordinary food, in which it is always present in appre- 

 ciable amount. Green vegetables of course contain it, as an ingre- 

 dient of their coloring matter. Since hemoglobine exists to some 

 extent in muscular tissue, it will be present in a more or less altered 

 form, but still containing iron, in most kinds of animal food. Accord- 

 ing to the analyses of Moleschott, 500 grammes of beef (about one 

 pound avoirdupois) will contain 0.035 gramme of iron; and iron is 

 also found in even larger proportion in rye, barley, oats, wheat, peas, 

 and especially in strawberries. As the quantity of this substance daily 

 discharged in the urine and with the bile is so small, we must regard 

 the greater portion of that which passes through the system as used 

 in the growth of the hair ; and a very moderate amount contained in 

 the food must be sufficient for the daily requirements of nutrition. 



Melanine. 



In all the dark-colored tissues of the body, in the choroid coat of 

 the eyeball, the rete Malpighi of the skin in the black and brown races 

 and in all individuals of dark complexion, in the hair, and in the 

 substance of melanotic tumors, there exists a coloring matter known 

 as melanine. When isolated or when collected in compact masses, it is 

 of a very dark blackish-brown color ; but by its mixture, in different 

 proportions, with other colorless or ruddy semitransparent elements of 

 the tissues, it may produce all the varying grades of hue, from light 

 yellowish-brown to an almost absolute black. It is deposited in the 

 substance of the animal cells in the form of minute granules, and is 

 usually more abundant in the immediate neighborhood of the nucleus, 

 when one is present, than near the edges of the cell. 



Melanine has not yet been obtained in a perfect crystalline form, and 

 its chemical characters are not completely determined. It is known, 

 however, to be a nitrogenous substance. As the average result of vari- 

 ous analyses collected by Hoppe-Seyler, 1 it contains, freed from ashes, 

 the following proportions, by weight, of carbon, hydrogen, nitrogen, and 

 oxygen. 



COMPOSITION OF MELANINE. 



Carbon 54.39 



Hydrogen " 5.08 



Nitrogen 11.17 



Oxygen 29.36 



100.00 

 According to Kiiline 2 repeated observations show that it also con- 



1 Handbuch der Physiologisch- und Pathologisch-Chemischen Analyse. Berlin, 

 1870, p. 177. 



2 Lehrbuch der Physiologischen Chemie. Leipzig, 1868, pp. 365, 442. 



