It is obviously impossible to draw definite conclusions as to the significance of the differences between our work and Gye's, and still less, of the differences between Gye's work and that of Murphy and of Flu. We can only say that in a fairly large series of experiments, extending over a period of 12 months, we have had absolutely no indication of the necessity of two factors in the production of the Rous sarcoma. In other words, we have been unable to duplicate either the results of Gye or the modified confirmations of his work by Murphy and Flu. We have shown that uncontrollable local and individual variations may produce results in occasional chicks which simulate satisfactory experiments, but when viewed as a whole, mean nothing. Because of the conflicting nature of results obtained by those who have undertaken to repeat the work, and on account of the difficulty of controlling all factors involved, we do not feel that it may be stated definitely that Gye's theory of the cause of cancer is wrong. On the other hand the theory apparently needs more evidence in its support if it is to receive further serious consideration. It is suggested, in order to untangle the subjéct as rapidly as possible, that future publications should include sufficient consecutive protocols to make the trend of the experiments obvious to the reader.

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