RosnAR( n .)n Plant Tumors ^97 



of another paper published in Science,"'' originally an address 

 delivered before the Washington Academy of Sciences on May 11, 

 1916, had been circulated. Smith had said that the full title of the 

 last paper should be " Further Evidence that Crown Gall is Cancer, 

 and that Cancer in Plants because of its Variable Form and its 

 Bacterial Origin offers Strong Presumptive Evidence Both of the 

 Parasitic Origin and of the Essential Unity of the Various Forms 

 of Cancer Occurring in Man and Animals." Any one of these 

 studies may have been read by Dr. Mayo and evoked his tribute 

 to Smith's work. But, since on February 15 Dean and Director 

 A. F. Woods — soon jo be President Woods of the Maryland State 

 College of Agriculture — informed Smith that he planned to be in 

 Rochester, Minnesota, the following Saturday and would take with 

 him a copy of a recent paper by Smith and present it to Dr. Will 

 Mayo, probably the study which Dr. Charles Mayo had read was 

 " Mechanism of Tumor Growth in Crown Gall." 

 In this study, Smith had concluded that 



it would seem . . . that in local osmotic action (possibly in some stages 

 chemical action also) of various substances (aldehyde, acetone, alcohol, 

 acids, alkalies) thrown into cells and diffusing from them in various direc- 

 tions, as the result of the metabolism of a feeble intracellular parasite or 

 symbiont together with the resultant counter movements of water and food 

 supply we have, in crowngall at least and presumptively also in animal 

 neoplasms, the explanation of tumor growth — that is, of that extensive 

 multiplication of cells in opposition to physiological control which has so 

 long puzzled pathologists and all students of overgrowths. 



In crowngalls, [he began by saying (pp. 167-168),] the removal of 

 growth inhibitions is brought about, I think, by the physical action of sub- 

 stances liberated within the tumor cells as the result of the metabolism of 

 the imprisoned bacteria. ... If the cell proliferation in crowngall is due 

 to substances liberated within the cell by the parasite, as it seems reasonable 

 to suppose, they must be substances either identical with or at least not 

 differing greatly in their physical or physiological action from those acting 

 on the non-parasitized cell during normal growth and division. ... In our 

 search for tiie direct exciting cause of tumors we need consider only the 

 excretions of known tumor-producing organisms; but since little or nothing 

 is known concerning the growth-exciting substance, or substances, produced 

 in animal neoplasms, or liberated in plants by the various gall-forming 

 fungi, or by gall flies and gall nematodes, we may for the present confine 

 our attention exclusively to the bacterial tumors of plants. This narrows 

 down the problem to a few species of bacteria and even some of these — 



"43(1121): 871-889, June 23, 1916. 



