AN AVIAN TUMOR IN ITS RELATION TO THE 



TUMOR PROBLEM. 



By PEYTON ROUS, M.D. 



(Read April 19, 191 2.) 



The behavior of malignant tumors has stimulated many hypothe- 

 ses as regards their causation and yet in some of its phases has 

 appeared to disprove all. The suggestions afforded by other normal 

 or pathological growth processes lead in numerous and diverse direc- 

 tions. Today, despite an immense accumulation of data, the solu- 

 tion of the tumor problem waits upon fresh findings ; and to fore- 

 tell the line of research which will yield these findings has not 

 seemed possible. 



The successful transmission of neoplasms of the lower mammals, 

 a few years ago, seemed at first to carry with it the immediate solu- 

 tion of the problem. But this did not prove to be the case. In order 

 to obtain a tumor-strain for investigation, an animal wnth a " spon- 

 taneous " tumor was required ; and the transmission of the growth 

 was soon found to involve a transplantation process, — as genuine a 

 transplantation as that of skin or other normal tissue. A new 

 tumor in the strict sense was not thus engendered, but to a portion 

 of the old another host was given. All efforts to separate out a cause 

 for the neoplasm or to transmit it by other means than by graft of 

 the living neoplastic cells were unsuccessful. The consistently nega- 

 tive results of such work, together with the general behavior of the 

 transplanted neoplasms, have led many investigators to forego the 

 idea of an extrinsic cause for malignant tumors in general and to 

 attribute them to some inherent cell-perversion, or else to a cell-de- 

 rangement precipitated by factors temporarily active. But it may be 

 pointed out that the basis for such a conclusion so far as it rests 

 upon experiment, rests upon work with the tumors of few species, 

 Those of the rat and mouse have been employed almost exclusively. 



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