526 PRINCIPLES OF VETERINARY SURGERY 



ized in the skin and hairs, is deposited in the tissues. But 

 this theory does not explain the existence of melanotic tu- 

 mors in animals with pigmented skins,— bay horses, black 

 horses, etc., — and their absence in albinotic animals. 



Melanosis has been the subject of numerous anatomo- 

 pathological and chemical investigations. Lebert, Robin 

 and Broca have described numerous melanotic tumors in 

 man; Virchow and Kindfleisch fibromatous, sarcomatous 

 and carcinomatous melanotic tumors. Carnil and Trasbot, 

 in 1867, published an important note on melanosis in the 

 horse. 



Robin's chemical study of melanosis, pursued with such 

 success, has recently been completed by investigators who 

 determined its composition. 



MELANIN. — Physico-chemical Character. — Melanin is 

 an organic substance, semi-solid, pultaceous, dense or con- 

 crete, brittle, easily pulverized after desiccation, and found 

 in normal organs (choroid, etc.) in the form of very small, 

 rounded granules (i to 9 microns) and in pathological 

 states, in the form of irregular bodies, consisting of an ac- 

 cumulation of the granules. Its color varies from black to 

 reddish or deep brown. It has neither taste nor smell, and 

 putrefies slowly and with diflficulty when exposed to the 

 air. When burned it emits an empyreumatic odor and is 

 converted into carbon. 



Melanin is chiefly characterized by its fixity and insolu- 

 bility in most of the reagents, cold or hot water, alcohol, 

 ether, dilute mineral acids and concentrated acetic acid. It 

 is feebly soluble in certain weak organic acids, such as uric 

 acid. It is soluble in cold ammonia, potassium, sodium and 

 the alkaline carbonates. Hippomelanin is insoluble in these 

 same reagents, but is dissolved by boiling alkalines. Hy- 

 drochloric acid precipitates the melanin and hippomelanin 

 .in these alkaline solutions. Chlorine decolorizes melanin 



