202 ROUS— AVIAN TUMOR IN ITS RELATION [April 19, 



The findings here to be presented were obtained in the study of 

 a mahgnant tumor of the chicken, which closely resembles in its 

 general characters the mammalian neoplasms, including those of 

 man. That such growths exist has been generally recognized ; and 

 their status as true tumors has been established. But like the neo- 

 plasms of other birds, of reptiles, amphibians, and many mammals, 

 they have remained almost unutilized for research. Our tumor of 

 the fowl proved transplantable and has thus far been observed in 

 several hundred chickens. It is a connective-tissue growth, a 

 spindle-celled sarcoma. From its tissue there has been isolated a 

 causal agent, ultramicroscopic in some, perhaps in all, of its forms, 

 and undoubtedly a living organism. Though the agent gives rise 

 to the sarcoma, and accompanies the growth, it does not take any 

 obvious share in the disease phenomena. These are referable to the 

 behavior of the neoplastic cells, a point now to be illustrated. 



The original sarcoma arose in a young fowl of pedigreed, pure- 

 blood stock, and its transplantation was successful only in this 

 fowl's blood-relations. A similar peculiarity has been often ob- 

 served on the transplantation of normal tissues, but it has not been 

 noted in association with the transmission of diseases caused by a 

 parasite. After propagation in several successive hosts, the sar- 

 coma became less precise in its demands and could be transplanted 

 to non-related fowls of the same variety. But like certain delicate 

 tumors of mammals it was for a long time transmissible only within 

 the limits of this variety, and at the latest test still grew most readily 

 in such hosts. All attempts to transmit it to animals of other species 

 have failed. 



A transplantation of neoplastic tissue is involved in the growth's 

 transmission under ordinary circumstances, and only by special 

 means has it been shown to be unnecessary. Ordinarily when bits 

 of the sarcoma are placed in a new and susceptible host they survive, 

 are vascularized, and proliferating, form a new tumor. The multi- 

 plication of the implanted cells obviously suffices to produce the neo- 

 plasm. In the histological pictures there is no indication that the 

 elements of the host ever become incorporated as true neoplastic 

 tissue. No tumor arises in hosts so unfavorable to the engrafted 

 tissue that it dies. 



