622 Third European Journey 



he suggested that the virus might have been " introduced with the 

 heated cancer serum they used along with the PM. The more so," 

 he added, " because, except in the first-generation tumor, they have 

 not succeeded in re-isolating PM." But he admitted that " an 

 independent investigator in a great institution for Serum Cultures 

 where the greatest exactitude is habitual " had gone far toward 

 confirming the Berlin work. This investigator had " injected into 

 rats pure cultures of PM {ivithout any cancer serum, but with 

 Kieselgur) and . . . obtained the same malignant tumor as they 

 did in Berlin." Two malignancies, transplanted through five and 

 six generations, were important, even though fifty rats were used 

 in the experiment, in view of the difficulty of transplanting a 

 tumor successfully from " any animal to one of another species " 

 and since it was not likely that the rats were of " any specially 

 susceptible race." Smith was learning of other new experiments 

 on animals in which in one way or another BacteriuTn tumefaciens 

 was involved. The experience was " highly exciting," but he 

 insisted " we must wait for more work to be done and for con- 

 firmation from other laboratories." ^''" 



He had not seen " plant tumors due to L but it [was] possible 

 [he might] see some on [their] return to Berlin," since seedling 

 sunflowers had been inoculated with L seven days previously. 

 When he got there, he found that the last set of 29 inoculations 

 on sunflowers, made twenty-one days before, with PM had de- 

 veloped " 28 good tumors and one small tumor." '°^ These were 

 " more than double the size of those [he had obtained] before 

 [he] went to Dresden," and he was given two specimens by Miss 

 Meyer. He looked also at the young sunflowers inoculated with 

 Hu, L, and three other strains four days before he went to Dresden. 

 On one of Hu there was a slight tumor; on L there was '" nothing 

 very definite but some callous tissue in the lancet cleft of the stem 

 that may later develop as a tumor. Judged by this," he wrote,"* 

 " L is losing its power to produce tumors in plants. I am eager to 

 see these plants on Monday, probably our last day here." But 

 nothing further was said in his journal about the L inoculations 

 or those of any other strain except PM. 



As president of the American Association for Cancer Research, 



102 



Written at Dresden, Mar. 3, 1925. 

 "^ Letter to Dr. W. A. Taylor, written at Berlin, Mar. 5, 1925. 

 "" Journal, Mar. 6, 1925. 



