Neoplasms in Horses Liver. 549 



Melanoma. Melanosis of the liver is comparatively frequent, 

 especially in gray horses, and above all when they are aging and 

 passing from dark gray to white. In many cases a more certain 

 diagnosis can be made than in sarcoma for the reason that primary 

 melanotic neoplasms are especially likely to occur on or near the 

 naturally dark portions of the skin, as beneath the tail, around 

 the anus or vulva, in the perineum, sheath, eyelids, axilla, etc. 

 The extent of the disease is likely to be striking, the liver, next 

 to the spleen, being the greatest internal centre for melanosis. 

 The whole organ may be infiltrated so that in the end its outer 

 surface is completely hidden by melanotic deposit. The surface 

 deposits tend to project in more or less rounded, smooth masses 

 of varying size according to the age of the deposit and the 

 rapidity of its growth. Individual deposits may vary in size from 

 a pea to a mass of 40 or 50 lbs. They are moderately firm, and 

 resistant, and maintain a globular or ovoid outline. The color of 

 the melanotic deposits is a deep black with a violet or bluish tint. 

 If the pigmentary deposit is in its early stage it may be of a dark 

 gray. The deposits are firmer than the intervening liver tissue 

 and rarely soften or suppurate. 



Melanosis in the horse is not always the malignant disease that 

 it shows itself to be in man, and extensive deposits may take place 

 externally and considerable formations in the liver and other in- 

 ternal organs without serious impairment of the general health. 

 It is only in very advanced conditions of melanosis of the liver 

 that appreciable hepatic disorder is observed. If, however, there 

 is marked enlargement of the liver, in a white or gray horse, 

 which shows melanotic tumors on the surface, hepatic melanosis 

 may be inferred. 



Lymphadenoma. Adenoid Tumor. I/ienaux describes cases of 

 this kind in which the liver was mottled by white points which 

 presented the microscopical character of adenoid tissue, cells en- 

 closing a follicle and a rich investing network of capillaries. 



Angioma. These are rare in the horse's liver, but have been 

 described by Blanc and Trasbot as multiple, spongy tumors on 

 the anterior of the middle lobe, and to a less extent in the right 

 and left, of a blackish brown color, soft and flucuating. The 

 largest mass was the size of an apple, and on section they were 

 found to be composed of vascular or erectile tissue. The tendency 



