TUMORS. 



315 



y stimulates them to grow 



relatively slow. Operation usuall 

 more rapidly. 



^ Melanosarcoma.— A melanosarcoma is any variety of sarcoma 

 in which melanin is deposited in the tumor cells. These tumors 

 are quite prevalent. Gray horses seem to have a special predis- 

 position to them, but they are also found in bay and black horses, 

 black or red cattle, black hogs, and, in fact, all varieties of do- 



Fig. 170. — Melano Sarcoma of hr>g skin. 



mestic animals regardless of color. On microscopic examination, 

 melanin is found deposited in the tumor cells. The melanin may 

 be in masses or granular and occasionally it may be found out- 

 side of the cells. Excepting the deposit of melanin, these tumors 

 have the same microscopical apoearance as the round or spindle- 

 cell sarcomata described before. 



