534 PRINCIPLES OF VETERINARY SURGERY 



1st. Melanotic tumors or melanotic infiltration of tu- 

 mors. 



2nd. Melanosis, properly so called, simple melanosis, 

 or melanotic infiltration of the tissues, with or without sub- 

 sequent neoplasia. 



Melanotic Tumors. — The history of this form of melan- 

 osis is confused with that of tumors in general. There is 

 but one additional element, the pigment. In some of these 

 tumors is found a structure analogous to the melanotic nod- 

 ule, which is subsequently described as a manifestation of 

 simple melanosis. The fundamental difference lies in the 

 preponderance of cellular proliferation, and the embryonic 

 character of the proliferated cells belonging to the melanotic 

 neoplasm. In other words, the melanotic tumors have the 

 evolution and the characters of special tumors infiltrated 

 with melanotic substaiace. The fundamental cells are very 

 variable. Sometimes they are embryonic connective tissue 

 cells, sarcomatous, fibromatous or myxomatous, while at oth- 

 er times they are epithelial cells of different forms distributed 

 through the alveoli (melano-carcinomata and melano-epi- 

 theliomata). The pigment is found distributed in abundance 

 in the connective stroma and new-formed cellular masses, 

 where it assumes the form of round spots or disseminated 

 islets similar to those of the melanotic nodules already des- 

 cribed. Their growth is rapid, and they generalize rapidly 

 through the medium of the lymphatics. Cachexia may su- 

 pervene from the neophasia, but not from the melanism. 



Dexter found a melano-sarcoma of the cardiac lymph 

 glands of the horse, but they may be located in the cardiac 

 septum. The tumors may generalize. Mawri reports a 

 small tumor on the tail that recurred twice after ablation, 

 and that was eventually followed by manifestations of par- 

 aplegia. The patient died and the autopsy revealed a tumor 

 in the neural canal at the third lumbar vertebra. The cord 



