426 TUMOUKS. 



creased activity by the blood, which one may suppose is highly 

 charged with the ingredients from which pigment is formed. 

 This would be merely an exalted natural action of the cells ; but 

 when the pigmentary matter is formed by the cells of glands, or 

 other structures than skin, we must look upon the process as a 

 perverted formative action. 



Melanosis appears usually as a rounded tumour, small at first, 

 but gradually enlarging in every direction within and upon those 

 portions of the body which do not lose their black colour by age ; 

 or several of these small tumours may manifest themselves simul- 

 taneously, enlarging by growth and by coalescence, and thus form- 

 ing one large tumour. Other tumours form in the neighbourhood, 

 and usually extend along the direction of the hairless skin of the 

 tail, anus, and perinaeum, until at last there is a most unsightly 

 collection of them, like bunches of large onions. After a time 

 they wither in their centre ; the skin ulcerates by a slow, degene- 

 rate, and non-suppurative process — being seemingly converted 

 into melanotic matter — and allows more or less of the contents of 

 the tumour to escape. As the tumours grow the natural tissue of 

 the part withers, its place being taken up by the melanotic matter. 



The animal does not seem to suffer much inconvenience, except 

 from the effects of friction upon the surface of the tumour when 

 it comes in contact with contiguous parts. Thus a tumour on 

 the tail will become sore if it presses upon another tumour on 

 the vagina, or if by its weight it presses heavily upon the oppos- 

 ing healthy skin, or when the tumour or tumours are so heavy as 

 to prevent the animal from elevating its tail during progression. 



Without entering further into the details of the symptoms, it 

 may be concluded that a black tumour in any part of the body 

 may be call'ed melanosis. 



Melanotic growths are neither very hard nor very soft, especi- 

 ally the external ones. Those found in the internal parts of the 

 body are much softer. The colour varies in shade from a dark 

 brown to the deepest black. 



Melanosis is generally confined to aged animals, but I have 

 seen it manifested in a five-year-old grey horse, and become 

 rapidly developed in various parts of the body. 



The treatment of melanosis is early removal, when it, as well 

 as other malignant growths, may be checked for a time ; but, as 

 already stated, its recurrent nature is so great as to preclude the 

 hope of permanent eradication. 



