74 BACTERIA IN RELATION TO PLANT DISEASES. 



form them, since the circulation in plants is not as well adapted as in animals to this sort 

 of migration. The stages outlined above take place with great rapidity since in very sus- 

 ceptible tissues, e. g., young, rapidly growing sugar-beets, it is possible by means of a few 

 needle-pricks to obtain a tumor as large as a man's fist in 5 or 6 weeks. 



These phenomena represent to me an entirely new type of bacterial disease. They 

 seem to me also to throw a flood of light on the mechanism of the development of malignant 

 animal tumors, making it likely that they also are due to parasites having similar relations 

 to the cells of man and the lower animals. 



The facts underlying this hypothesis may be summarized as follows : 



(1) The crown-gall disease is of bacterial origin beyond reasonable dispute, as shown 

 by hundreds of poured plates and pure culture inoculations. It is also a neoplasm rather 

 than a granulomata (vide evidence advanced in Bulletin 213). 



(2) The bacteria can not be found readily in the tissues by means of microscopic 

 examinations although the poured-plate method shows that they occur there, and the vessels 

 and intercellular spaces being free from any granules whatsoever, the bacteria must occur 

 inside of the cells, forming some portion of the cell-inclusions. 



(3) The poured plates confirm the microscopic examinations. They show that the 

 bacteria are not abundant in the tissues. They also show that these bacteria often occur 

 in the tissues of the tumor in a moribund state, requiring 4 to 6 days or more to recover and 

 develop colonies on the agar, although when once recovered they grow in second and sub- 

 sequent transfers as promptly as other organisms. 



(4) In flasks containing water, peptone, grape-sugar, and calcium carbonate the 

 organism (from the daisy) produces an abundance of acetic acid. 



(5) Chemical analysis shows an excess of acid in the tumor tissue as compared with 

 sound parts of the same plants (daisy, sugar-beet), but up to this date a sufficient quantity 

 of the tumor for a definitive quantitative test (10 kilos or more) has not been available. 

 If acetic acid is formed in the tumor cells, it must be in minute quantities, and it might be 

 oxidized by some subsequent action of the host protoplasm so as not to be recoverable on 

 chemical analysis. 



(6) In artificial cultures club-shaped, Y-shaped, and variously branched bodies can 

 be produced at will by adding small quantities of acetic acid. 



(7) Similar forms occur in the tissues of the tumor, and while I have not seen them in 

 the cells they can be obtained on sterile slides in small numbers by making sections of tumors 

 and allowing them to diffuse in sterile water for a few minutes. 



(8) When too strong a dose of acetic acid has been added to the agar, or bouillon 

 cultures, the Y's and other involution forms can not be resuscitated by means of agar poured 

 plates, but when the dose has been properly adjusted a portion of the bacteria may be 

 recovered in poured plates, the colonies coming up slowly the same as when material is 

 taken from the interior of the tumors. 



(9) Finally, the statements respecting the tumor strand, the anatomy of the secondary 

 tumors, and the occurrence of the bacteria in these latter are supported by many observations 

 and experiments. 



Schiff-Giorgini first clearly recognized metastasis in the olive, although earlier Savas- 

 tano pointed out that some tubercles develop superficially and others from the deep tissues. 



