624 Third European Journey 



still other errors were possible: unknown natural tumors in the 

 rat " already in process of development " or the pyramiding of a 

 " number of successful malignant tumor transplants upon a very 

 slight basis, perhaps on only one primary tumor " due perhaps to 

 the virus. At least he was skeptical, and his skepticism persisted. 



Before leaving Berlin for Copenhagen, he called on Dr. Otto 

 Appel, director of the Biologische Anstalt, and found the Anstalt 

 " greatly enlarged " since 1906 when he had first conferred with 

 Director Rudolph Aderhold and when Dr. Appel was first assist- 

 ant. Now a great agricultural research institution, with more than 

 fifty branches of work and five substations, an expanded museum, 

 and many other improvements, had been developed. Dr. Appel 

 questioned Smith closely on many points and introduced him to a 

 bright, young bacteriologist, Dr. Carl Stapp, who was working on 

 crown gall and various other plant diseases. He showed Smith 

 "good tumors of crown gall on potato tubers and stems, obtained 

 by dipping the tubers for a moment into the culture and then 

 planting them. [Smith}promised to send [him] various strains of 

 Bact. tumefaciens. [He] saw tumors of this [Smith's laboratory's 

 hop strain] growing on slices of carrot floating in water in sterile 

 Petri dishes." "^ 



On March 9 he said goodbye to Dr. Blumenthal and his assist- 

 ants and was told of a third rat tumor. Beta, from another breast 

 cancer; but it was not yet known whether the transplants would 

 take.^^" Miss Meyer told him that " she had tried in vain to culti- 

 vate bacteria from this breast-tumor resembling Bact. tinnefaciens 

 but she will continue to try. The difiiculties," Smith wrote,^^^ " are 

 great because there are many saprophytes and they grow rapidly 

 and overgrow the plates and swamp out all slow-growing bacteria 

 like Bact. tiimefaciens. This raises again the question whether 

 some virus carried over with Bact. tumefacieus may not after all 

 be the cause of the rat tumors. Miss Meyer evidently thinks the 

 bacteria are there." 



Dr. and Mrs. Smith left Berlin for Copenhagen on March 12, 

 he possessed of the valuable reprint given him by Dr. Otto 

 Warburg, " Ueber den Stofi^wechsel der Carcinomzelle," "^ which 



"'•Journal, Mar. 7, 1925. 



^^^ See, Some newer aspects of cancer research, op. cit., 601. 



"'Journal, Mar. 9, 1925. 



"' Op. c!t., at p. 578 of this book. 



