TUAIORS.. 321 



as in normal papillae or the fibrous tissue or the epitheHal tissue 

 may be in excess. Hence some papillomata are apparently sub- 

 epithelial fibromata and others are masses of epithehal cells 

 upon a very limited fibrous matrix. Papillomata have the 

 same relation to underlying structures that normal papillae 

 have. The stroma of the papillomata has a definite connection 

 with the dermis in cutaneous papillomata and the e])itheliurrt 

 apparently originates from the lower layers of the epidermis. 

 'lrans\-erse sections appear as areas of stroma surrounded by 

 epithelial cells, while epitheliomata are composed of columns of 

 cells surrounded by a stroma. 



These tumors are essentially benign. They mav result fatally 

 because of mechanical interference, as in the occlusion of the 

 oesophagus or the urethra. They ma)- undergo necrosis, thus 

 providing an entrance for infectiim and result in fatal septicemia. 

 Papillomata do not form metastases, but they are frequently 

 multiple. Cases have been recorded where the conditiun papil- 

 lomatosis has been transmitted from one animal to another, lly 

 constant irritation some epithelial cells may become enlarged in 

 the subsurface, thus providing a centre from which an epithe- 

 lioma may develop. They respond to medicinal treatment and 

 surgical interference. 



e;mbryonic EPITITELIAL tptmoi^s. 



This is a group of tumors composed of embryonic epithelial 

 cells, and for description mav be divided into three varieties, — 

 (1) carcinoma, (2) epithelioma, and (3) adenoma. 



Carcinoma is an epithelial tumor characterized by the gnaip- 

 ing of cells into nests or alveoli. They are of rather common 

 occurrence but not as common as sarcomata. Horses and mules, 

 cattle, sheep, hogs and dogs have been observed aftected -with 

 carcinomata. These tumors have no selective action for any 

 tissue. They have been found affecting mucous membranes, 

 glandular structures, invading muscles and even in bone. They 

 are usuallv diffuse, although they may be limited by a membrane 

 resulting from reaction of the surrounding tissue. They are 

 usually soft ( encephaloid) , but they may be quite hard (scir- 

 rhous), depending upon the amount of stroma or fibrous tissue 

 contained. The color of a cut section of a carcinoma is usually 

 gray, dirty-white or pale pink. They may be mottled because of 

 degenerating or necrotic centers or hemorrhage. Lobules may 

 be observed, especially in those carcinomata formed bA' the eel- 



