TUMORS IN FOWLS 269 
Autopsy of the bird reveals the presence of about 20 cc. of a thin 
straw colored fluid in the peritoneal cavity. Attached to the lower 
margin of the liver, to the oblique membrane, and to the parietal 
peritoneum are many firm, pale yellow, ovoid globular nodules, the 
largest about 1 cm. in diameter. On section these resemble the 
nodule in the left breast, except that in them the necrosis is irregu- 
larly distributed. At the pelvic region, where several of the masses 
have coalesced, softening and necrosis are extensive. No growths 
are visible in the other organs. 
Microscopic examination of the tumor reveals it to be a spindle- 
celled sarcoma. -In a typical section there are observed loose bundles 
of spindle cells coursing in every direction, and separated from the 
lesser blood vessels only by endothelium. Where such a bundle is 
cut transversely, the appearance is that of a group of round cells of 
varying sizes. 
Transplantation of the tumor was accomplished by the use of 
fowls from the small, intimately related stock in which the growth 
appeared originally. Young chickens were more susceptible than 
adults. Market fowls of similar variety proved insusceptible as did 
pigeons and guinea pigs. During the first four generations, the 
tumor remained true to type and was infiltrative and destructive. 
Metastasis to the heart was observed once. 
The tumor has been found to be transferable by the filtrate of a 
Berkefeld filter. 
Rous has shown that ultraviolet light rapidly kills the cells of this 
transplantable sarcoma of the fowl without notably injuring the 
etiological agent associated therewith. The Roentgen ray has little 
effect on either cells or agent. 
He observes that fowls manifest two sorts of resistance to the 
avian tumor, one directed against the implanted tumor cells as such, 
the other against the action of the etiological agent to cause a neo- 
plastic change. In the individual fowl the two resistances appear 
to be independent of one another, though they may exist together or 
may both be absent. A recognition of them will perhaps explain 
some features in the biology of other tumors. 
Rous and Murphy observe that variations have from time to time 
occurred in the structure and behavior of this tumor. After a long 
series of transfers the growth frequently gave rise to fatal hem- 
orrhages from its substance. In some of the later, rapidly growing 
tumors the cells tended to be spherical, showing only a very tardy 
and imperfect differentiation to the spindle form. A giant-celled 
