244 ^- ^- RHOADS 



is invoked to explain the failure to do so from the cancer of cottontails. 



The conclusions drawn from the immunological evidence presented 

 concerning the papilloma virus and the cancer supervening upon it in 

 rabbits is that "the cancers result from virus variation, this in many in- 

 stances being slight" (lOo). This conclusion is arrived at because of 

 evidence for the complete specificity for the virus of the antibodies as- 

 sociated with the cancer, and the complete failure to derive any infec- 

 tious material whatever from the cancers following virus-induced papil- 

 lomas which are supposedly due to the virus. If the serological evidence 

 for the virus etiology of the cancer is to be accepted, then the virus 

 should be the one reacting specifically with the antibodies, and not a 

 modified one. If the evidence is not to be accepted, it is hard to support 

 the view that the papilloma virus is the etiologic agent. If some modifi- 

 cation of the virus is to be invoked as etiologic, then evidence in support 

 of the existence of a modified agent is required. This is advanced in a 

 recent communication by Kidd ( 1 1 ) announcing the demonstration in 

 the V2 carcinoma of an antigenically specific protein wholly distinct im- 

 munologically from the papilloma virus. Further studies will be of inter- 

 est as they concern the place of the virus in this picture. 



Support for the theme of a virus, or extraneous, infectious parasitic 

 etiology for the cancer in rabbits following the virus-induced papilloma 

 is further sought in immunologic studies of the Brown-Pearce trans- 

 plantable cancer in the same species (10). There was obtained from this 

 tumor a serologically active substance, demonstrable by its ability to fix 

 complement (no agglutination or precipitin reaction was noted) which 

 was insoluble in alcohol, was inactivated by heating to 65° for 30 min- 

 utes, by treating with acid to pH 4.5 or lower or alkali to />H 11.5 or 

 higher, with a uniform particle size over 348ja, and centrifuged down 

 by 20,000 r.p.m. for one hour. These general characteristics of a large 

 protein molecule with the ability to fix complement in the presence of a 

 specific antibody are advanced to favor the infectious etiology of the 

 tumor, though no infectious agent was obtained from it. 



The matter of immunologic specificity of neoplastic cells is one of 

 great interest and importance. Beyond doubt new methods and new ex- 

 periments are desirable. The studies of Andrewes (102) and of Fouldes 

 (103) should be consulted in this regard. These investigators proved 

 that substances related antigenically to the chicken-tumor agents are 

 present in certain fowl tumors elicited with carcinogenic chemicals. The 

 latter have not been proved to be filterable, however, and hence the ob- 

 servation tells us only that the induction of cancer by a carcinogen 



