CHARACTER OF THE TUMOR. 171 



e. g., in involution forms. In tliis connection see a paper by S. B. 

 Wolbach and Tadasu Saiki on the presence of bacteria in normal 

 livers, demonstrable by cultural methods but not by stains (The 

 Journal of Medical Research, Boston, September, 1909, p. 274). 



(5) The likeness of crown-gall to animal tumors might be thought 

 at first sight to be lessened, owing to the fact that plants of many sorts 

 can be made to take the disease by means of grafting or pure culture 

 inoculation, whereas animal tumors are supposed to be very restricted 

 in cross-inoculability. One reason for this difference may lie in the 

 greater simplicity of plant structures, plants being much less highly 

 specialized than vertebrate animals. It is possible also that the 

 doctrine of non-cross-inoculability of animal tumors may be a sweeping 

 generalization based on insufficient evidence. Recently Van Dun- 

 germ states that he has successfully inoculated sarcoma of the rabbit 

 into the hare; and Sticker claims to have produced dog tumors in 

 the fox. 



(6) The most difficult thing to explain on any parasitic theory is 

 the character of the metastases in cancer. These are so cha; acteiistic, 

 and so like the tissues of the original tumor that from an examination 

 of sections of the secondary tumor it is often possible to determine 

 where the unseen primary tumor is located, whether, e. g., in the 

 stomach or the ovaries. This, however, does not seem to be an in- 

 superable objection. Vide Aliihlman, Ueber Bindegewebsbildung, 

 Stromabildung und Geschwulstbildung — Die Blastocyten Theorie 

 (Archiv. f. Entwdckelungsmechanik, 28 Bd., pp. 210-259). 



It is not yet beyond dispute that a cell mother of one kind can 

 never give rise to a cell of another kind when a changed stimulus is 

 applied. Adami and several others maintain that particular animal 

 cells forming a normal part of tissues, i. e., not in juxtaposition with 

 the proliferating mass of morbid tissue, may become cancer cells. 



METASTASES. 



It had been noticed during the early part of our work with the gall 

 organisms that when a daisy plant, never before affected, was inocu- 

 lated and galls were produced, the disease did not confine itself to the 

 inoculated part or its immediate neighborhood, but made its way to 

 other parts of the plant. This was shown by the marked tendency 

 of galls to form on leaves or parts of the stem other than that part 

 on which galls developed as the result of our inoculations. 



Some of these galls may have been due to accidental surface 

 infections, but it seemed that all of them could not be ascribed to 

 local surface infections for several reasons, 1. e., because the check 

 plants in the same house remained remarkably free from infection, 

 because the hothouse was quite free from small animals likely to cause 



213 



