CHAPTER XIV. 

 MELANOSIS. 



SOLIPEDS. 



The name "melanosis" is applied to a morbid condition 

 characterized essentially by the overproduction of pigment, 

 with or without neoplasms. The term signifies abnormal 

 pigmentation of the tissues by a substance known as melan- 

 in. This substance may accumulate in any part of the con- 

 nective tissues of the body,— the derma, the intermuscular, 

 interfascicular, subcutaneous, or the interstitial connective 

 tissue of any of the organs. It may infiltrate organs and 

 form into more or less voluminous masses known as mel- 

 anoses, or form into neoplasms called melanotic tumors. 

 In some cases it forms little projecting grains around the 

 anus, while in others it forms into tubercles which are 

 found in the lungs, the lymphatic glands, the liver, the spleen, 

 etc. Still others develop into voluminous tumors. The 

 tumors are usually simple, that is to say, they are deprived 

 of all neoplastic tissue, the melanin deposited in the pre-ex- 

 isting tissue, forming the entire tumor. 



Sinaple melanosis and melanotic tumors are found in the 

 horse, the mule, the ox, the sheep, the hog, and the dog. 



HISTORY. — The word "melanosis" was not used be- 

 fore the beginning of the present century. Laennec, in 

 1806, regarded melanosis as a variety of cancer, which opin- 

 ion was held by Trousseau, Le Blanc and Cruveilhier. In 

 1826, Breschet attributed the origin to the effusion of blood 

 into the tissues. Brugnone, in 1871, and Gohier, in 1813, 

 etc., drew attention to its frequency among white horses, 

 thus leading veterinarians to look upon it as a manifesta- 

 tion of an aberration of the pigment, which, not being util- 



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