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. 
a 
