166 CROWN-GALL OF PLANTS. 



light of cancers is the fact that we know them to be produced by a 

 specific organism, hence they are granuloraata. If we did not know 

 them to be so induced, tlien they would be willing enough to consider 

 them as tumors. This is shown by the fact recently called to our 

 attention, i. e., after these pages were prepared for the printer, that 

 in the International Conference on Cancer at Paris in October, 1910, 

 Professor Jensen (of mouse-tumor fame), not knowing of our re- 

 searches, presented without hostile criticism a paper (Von echten 

 Geschwiilsten bei Pflanzen) on the crown-gall of the beet, in which 

 he maintained it to be not onl}^ a true neoplasm, but a genuine tumor 

 for which he predicted a role as important in cancsr research as the 

 mouse tumor itself has played. His exact words are: 



Obwohl meine Untersuchungen niir noch einen vorliiufigen C'harakterhaben, glaube 

 ich doch, aussprechen zxi diirfen, class wir beim "Wurzelkropf ' nicht nur mil einem echten 

 Neoplasmus sondem gar mil einem Tumor zu sc.haffen haben, dcr in geivissen Beziehungen 

 AehnlicJil-eit viit den malignen Geschwiilsten dcr Tiere darbietel; ja, ich bin geneigt zu 

 glauben, dass er in der Geschwulstforschung eine ahnliche Rolle spielen honnen wird, tvie 

 jetzt die Mimsecarcinome. — Page 248. 



And again, on page 254: 



Wir haben also in dem sog. Wurzelkropf eine Geschwulsthildxing vor iins, die aufeiner 

 andauernden, abnormen Proliferations/ahigkeit gewisser Zellen zu beruhen scheint, und 

 die nicht nur dadurch, sondern auch durch ihre Beeinflussung des Wachstums der Riibe, 

 ihre Fahiglceit zu rezidivieren und sich trans plantieirn zu lassen, so wie durch die abnormen 

 chemischen Verhaltnisse der Zellen so sehr an die malignen Tumorcn da- Tiere erinnert, 

 dass ein naheres Studium der biologischen Verhaltnisse der Geschiuulst unzweifelhaft wohl 

 angebracht ware. 



The animal pathologists have not come to any agreement as to 

 what is the cause of sarcoma, carcinoma, and similar tumors, some 

 holding them to be due to organisms, either known or suspected, 

 wliile others, now the majority, maintain that inasmuch as inocula- 

 tions of certain ground cancerous tissues have not led to any infec- 

 tions and inoculations of uninjured tumor tissues of the same sort 

 have led to numerous and repeated infections, therefore the disease 

 can be transmitted only by the living proliferating cancer cells, e. g., 

 experimentally by grafting. As clear a statement of this view as 

 any, perhaps, is that given by Diirck : 



The essential difference between infectious growths and genuine tumors is that 

 when the former are reproduced by metastasis the parasite itself is conveyed in the 

 blood and incites at the metastatic site new formation of tissue similar to that of the 

 parent growth, whereas in the case of genuine tumors metastasis takes place by the 

 transplantation of a part of the parent tumor, which then begins to proliferate inde- 

 pendently at the new site. 



But we are totally in the dark as to what originates cancer cells or 

 causes them to proliferate. 



It has been known for a considerable period, i. e., since 1900, that 

 crown-galls could be inoculated into healthy plants by means of 



213 



