562 Crown Gall-Animal Cancer Analogy 



giant cells. Many plants are killed by this tumor, and many others are 

 dwarfed so badly as to be worthless. It occurs on a multitude of hosts in 

 many parts of the world and has not received the attention it deserves. 

 Other destructive above-ground plant tumors are due to nematodes of the 

 genus Tylenchns. These occur on wheat, clover and other plants. 



While in Ann Arbor, Dr. and Mrs. Smith visited in the home 

 of Dr. and Mrs. Bradley Moore Davis. Dr. Davis was now a 

 professor of botany at the university and on December 11, the two 

 men conversed on the " possibility of destruction or modification 

 of some chromosome as [a] basis for the cell modification in 

 cancer." Smith asked Davis " if he accepted bud variation " in 

 plants, and his reply was " yes." ^^ In his address,®" Smith had 

 suggested that " some element of the cell or of its environment 

 which ordinarily acts as a break on cell division is destroyed or 

 weakened by the action of certain physical and chemical activities 

 (x-ray burns, common burns, arsenic, cobalt, tar products, products 

 of worms and of bacteria) and so we get a cancer, that is, a cell- 

 multiplication passing beyond physiological control." In 1922- 

 1923 he was planning some new experiments, and by 1926 he 

 was prepared to suggest in a formal paper on " Recent Cancer 

 Research " ®' the possibility of chromosomic destruction with a 

 subsequent abnormal affection of all descendants of all the cell 

 or cell-complex. 



There was another point in crown gall research about which 

 Smith was unwilling to venture a final opinion until later. He did 

 not disagree with C. O. Jensen that, in crown gall. Bacterium 

 tumejactens converts normal cells into tumor cells. But, on the 

 basis of a lack of scientific evidence at that time, he questioned 

 the conclusion that if the bacteria die out the cells still retain 

 and transmit their acquired characters. He awaited more corro- 

 borative evidence for the present view that once the genes within 

 the chromosomes have been changed from normal to tumor cells, 

 in crown gall the tumor cells without continued stimulus from the 

 bacteria will continue to grow indefinitely and autonomously. Yet, 

 before the end of his life, he candidly conceded that experimental 

 proof might be produced to show that cells could be so " ab- 



"" Smith's diary, Dec. 11, 1922, p. 345. 



*" Twentieth century advances in cancer research, op. cit., 315. 



" Amer. Naturalist 60(668) : 247, May- June. 



