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 (1910), an osteo-chrondro-sarcoma (1912), and a spindle- 
celled (intracanalicular) sarcoma (1913) 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 (1913). 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 *'^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 
