MELANOSIS 81 



MELANOSIS 2 



Pathologists tell us that melanosis is a form of cancer. ^ 

 The tumors or nodules presented in this condition are^^ 

 sajd_ to ^contain pigment. The disease affects white and 

 grey horses exclusively, appearing in the form of black 

 nodes or buttons in the region of the anus, the under side 

 of the tail, the sheath and penis, the eyelids, the lips, and 

 at times in the skin on various other parts of the body. 

 These nodes make their appearance at from the sixth to 

 the tenth year of the animal's life. They increase in size 

 slowly, but attain great dimensions, relatively, in very 

 old horses. In the anal region they are frequently seen 

 in clusters, occasionally in such numbers and of such 

 size that the anal opening is displaced or hidden. In 

 other parts of the body these tumors do not attain great 

 size nor appear in such great numbers as they do in the 

 anal region. 



The disease is.,without question^, hereditary. The get 



of a certain PercheroiThorse in this staEe^ most of which 

 were grey, are almost without exception affected with 

 melanosis. I have treated five or six of these horses, 

 and every one of them has from ten to thirty melanotic 

 tumors. 



Only rarely does melanosis cause serious, or even trou- 

 blesome, disturbances. In the anal region a melanotic 

 node may suppurate or break down, producing a mUd 

 periproctitis. The discharge from melanotic tumors is 

 at first a tarry, black paste. Later, ordinary pus mixed 

 with bloody streaks appears. In some instances the de- 

 velopment of a melanotic growth in the rectum or above 

 the rectum in the sacral region may attain such size that 

 it interferes with the fecal evacuations, either from direct 

 blocking of the rectal canal, or from pain produced dur- 

 ing the act of defecation. 



