498 BULLETIN OF THE BUREAU OF FISHERIES. 



rence of cancer in animals might be explained by the distribution of some nematode or 

 other carrier. 



Regaud (1907) reported two rats in one of which he found at autopsy a general 

 sarcomatosis of the peritoneum. At the border of the liver hung a cyst which contained 

 a cysticercus. The neoplasm was a sarcoma with fusiform elements. Inoculation into 

 five rats remained negative. The second, an adult male, having been found dying 

 without known cause, was killed. In the peritoneum a tumor the size of a nut had devel- 

 oped in the large omentum. There were numerous miliary granulations around the 

 tumor. At the center of it was a smooth cavity containing a tapeworm 25 centimeters 

 long and living. Intraperitoneal inoculations made in five rats were negative. The 

 parasites in both cases were identified as cysticerci of the Tseniacrassicola of the cat. In 

 common with Borrel, Regaud felt that the cysticerci in these instances were the carriers 

 of a virus, as he had frequently found cysticerci in the liver of rats killed for histological 

 research without accompanying neoplasms. 



That a virus of cancer is no longer hypothetical has been shown by the recent 

 demonstration by Peyton Rous in three varieties of sarcoma in chickens of a filterable 

 virus capable of producing type-true neoplasms. This agent passes through a medium- 

 grade Berkefeld filter. It is preserved by glycerin, has a killing point slightly higher 

 than the cells of the chicken, is not injured by freezing, and is killed at 55° C. The agent 

 can be preserved by drying the cells and can withstand grinding. After many months 

 the agent can be separated from the dried cells by filtration, or, in common with them, 

 on injection inaugurates at the point of trauma the growth of a malignant sarcoma of the 

 type from which the virus has been taken. Rous has separated the filterable virus from 

 a spindled-celled sarcoma (19 10), an osteo-chrondro-sarcoma (191 2), and a spindle- 

 celled (intracanalicular) sarcoma (191 3) with peculiar arrangement of the cells. The 

 virus of the osteo-chondro-sarcoma possesses the remarkable quality of causing the 

 connective tissue with which it comes in contact to proliferate and specialize by forming 

 cartilage and bone. His experiments not only show the existence in these tumors of a 

 filterable virus but the existence for each type of a special virus. It is needless to point 

 out that the agent of goiter is also filterable, which fact should strengthen the theory 

 that the goiter agent is a living organism and not a soluble toxin. 



Haaland, Loewenstein, von Wasielewski, and others have found helminthia in 

 mouse cancers. 



The theory of Borrel regarding nematodes has recently been experimentally proven 

 by Fibiger (191 3). Fibiger found in three rats in his laboratory large papillary growths 

 of the stomach, in all of which were many small nematode worms. These growths he 

 held to be fibroepithelial tumors, probably malignant, an opinion which was strengthened 

 by microscopic examination. The epithelial proliferation was found to have broken 

 through the muscularis mucosa, and the submucosa contained projections and islands 

 of squamous epithelium. To determine how frequent the disease might be in Copen- 

 hagen, he examined 1,144 r^-ts without finding any evidence of the disease. Later his 

 attention was drawn to cockroaches as possible carriers of such nematodes, through an 

 article by Caleb in 1878, who found nematodes in the stomachs of rats after feeding 



