52 SPECIAL EQUINE THERAPY 



When melanosis affects an eyelid it must be differenti- 

 ated from botryomycotic nodes. I have seen the two 

 conditions affect an eyelid simultaneously. 



Melanotic growths in the sheath may prevent normal 

 protrusion and retraction of the penis, resulting at times 

 in a severe paraphimosis. 



Obscure cases of lameness in aged white horses that 

 have melanosis may occasionally be attributed to pres- 

 sure from a melanotic tumor on a nerve trunk in the 

 parenchyma of a muscle in the affected limb. 



Traumatism in the immediate vicinity of a melanotic 

 tumor nearly always results in serious consequences. 

 Either the growth of the tumor is greatly stimulated 

 thereby, so that a previously passive nodule becomes a 

 rapidly growing, malignant tumor, or the wound itself 

 assumes a vicious and stubborn character. Apparently 

 the tissues surrounding such tumors are already sub- 

 normal in vitality and resisting power. 



Melanosis in horses under ten years of age is usually 

 passive. After the tenth year a passive melanoma in any 

 part of the anatomy may become active. This should be 

 considered in examining grey or white horses for sound- 

 ness. A thorough examination for soundness in grey or 

 white horses must always include examination of the 

 rectum, with the object of detecting the presence of mela- 

 notic growths in this canal. Their presence in, or sur- 

 rounding parts of, the rectum constitutes an unsoundness 

 in horses of any age. Some cases of rectal and anal 

 fistula have their origin in a degenerated melanoma. On 

 account of the hereditary nature of melanosis, the breed- 

 ing of horses affected should be discouraged. 



Treatment. None while passive. When an isolated, 

 single tumor becomes active in a region where a thorough 

 enucleation is possible, it should be dissected out and the 

 bed of the growth thoroughly cauterized. Simple dis- 



