TUMOURS. 421 



'^ cancer juice '' scraped from its surface. The manner of 

 extension and any infective indications will confirm the 

 diagnosis. These tumours exhibit all variations in size 

 and form as well as in consistence. 



Causes. — These growths are due to hereditary influence 

 and have been originated by inoculation. The latter 

 process is attended with much difficulty and cannot be a 

 frequent occurrence in nature ; we must, therefore, con- 

 sider hereditary tendency to be the predisposition, and we 

 find that mechanical and other injuries prove excitants. 

 Under these circumstances we cannot be surprised that ma- 

 lignant tumours are less frequent in the lower animals than 

 in man. Besides the above enumerated forms of cancer two 

 other kinds are to be included under this heading ; they 

 are less malignant than the others, and sometimes seem 

 to be simply local. 



Epithelioma consists of freely proliferating epithelial 

 cells embedded in a fibrous stroma. The cells present 

 must not be considered truly of an epithelial nature, but 

 rather mimic the cells of the tissue in which the tumour 

 grows, either the skin or mucous membrane. 



Melanosis, sometimes called '^ hlach cancer,*' is some- 

 what similar, but its cells resemble those of the Mal- 

 pighian layer of the skin which contain pigment in the 

 granular form. They differ from them, however, in their 

 high reproductive activity and in their tendency to in- 

 filtrate other tissues. Thus, melanotic infiltrations of 

 various organs sometimes are seen, but they are very rare 

 in the ox, in which animal, however, tumours of this black 

 cancerous material occur, and often are of very considerable 

 size. They differ from those of the horse in having a less 

 marked tendency to spread, and also in not having a pre- 

 ference for the anal and coccygeal parts of the body. 



Treatment of cancerous tumours is not satisfactory. 

 The constitutional tendency remains except in a local 

 case taken very early ; also there is a great liability to 

 recurrence. Excision is the only means of relief, and 

 all the morbid material must be removed. Cases of this 

 disease are not frequent in the ox but some are on record. 



