Neoplasms 381 



ing textures. When such an overgrowth of follicles tends to retain 

 the glandular form it is termed Adenoma, but when the overgrowth 

 is characterized by infiltration and development of an embryonic 

 type of cells it is termed Carcinoma. If both types are present 

 in the same tumor it is termed Adeno-Carcinoma. The histo- 

 genesis of cancer remains a mooted point. There are some who 

 zealously advocate the parasitic theory, and others who as ardently 

 oppose it. Still other authorities are willing to concede the pos- 

 sibility of a parasitic origin in the first instance sufficient in itself 

 to initiate the atypical cell proliferation, or so to speak, to start the 

 cells running wild on a wrong track, but suggest that the habit once 

 having been acquired may continue independent of the initial 

 stimulus. At the present time the majority opinion is against the 

 parasitic origin of the disease. Heredity is generally recognized 

 as a potent predisposing factor in the dog as in man, but it must 

 be remembered that the lineal and clinical histories of our patients 

 are seldom traceable with accuracy. It is recognized that benignal 

 adenomatous tumors offer conditions favorable to the development 

 of carcinoma. As they contain both glandular cells and connective 

 tissue cells it is easy to comprehend this capacity of transition. 

 The phenomenon might be aptly described as "progressive carcino- 

 matosis," and it is particularly prone to occur in consequence of 

 repeated injuries or prolonged continuous irritation. A typical 

 example is afforded by the following case which occurred in my 

 practice : A male hound, aged eight years, for some years had been 

 secured by a chain, one end of which was attached to a ring which 

 ran on a wire about forty feet long. In this manner the animal 

 was enabled to run to and fro within a limited area. On its right 

 side, as it left its sleeping quarters, was a high wall, while on the 

 other side, a short distance away, was its master's residence. Hence, 

 on running to and fro the length of the wire, it would invariably 

 get on the side looking towards the house, and it so happened that 

 the chain tended always to get between its front legs and rub 

 continuously on a certain spot on the posterior and inner aspect 

 of the right leg. About two years previous to the time the case 

 was brought to my notice, an abrasion was noticed on this spot, 

 which gradually gave place to a sessile fibrous growth which en- 

 larged slowly for eighteen months. It then suddenly began to in- 

 crease at a much more rapid rate, its weight causing it to become 



