THE DISCOVERY OF CAX'CER IX PLAXTS 



57 



certain other diseases which are known 

 to be of parasitic origin. 



Dr. Borrel, of the Pasteur Institute, 

 has found animal parasites (acarids) 

 buried in the cell masses of certain can- 

 cers of the face, and he conceives that 

 possibly these parasites introduce an or- 

 ganism or a poison much in the same 

 way as the mosquito introduces the ma- 

 laria virus into the system. Still more 

 recently (1911-1912) Dr. Peyton Rouse 

 has announced* that a chicken sarcoma 

 (cancer) is inoculable in the absence of 

 cancer cells, and that the tumor material, 

 even when dried for six months, is still 

 infectious. 



THE LATEST DISCOVERY 



But perhaps the strongest support of 

 the parasitic theory of cancer has come 

 from what at first sight would seem to 

 be the most unlikely source, namely, the 

 Bureau of Plant Industry of the U. S. 

 Department of Agriculture. This, how- 

 ever, is not so remarkable when we re- 

 member that cancer is a disease result- 

 ing from abnormal cell stimulation, and 

 that the cell is substantially the same in 

 both plants and animals. 



Indeed it is to comparative pathology 

 that we must look for the most striking 

 results of our future investigation. 



For some nine years past Dr. Erwin F. 

 Smith, the pathologist in charge of the 

 Laboratory of Plant Pathology of the 

 Department of Agriculture, and his as- 

 sistants have been conducting a series of 

 investigations into the origin and his- 

 tology of the crown gall. 



The crown gall is a plant disease which 

 causes an annual loss to farmers of mil- 

 lions of dollars and has become a serious 

 problem to the agriculturist on account 

 •of the number of species of plants liable 

 to its ravages. It is known to attack the 

 daisy, the almond, peach, and other stone 

 fruits, the apple, quince, raspberry, black- 

 berry, the rose, the grape, red clover, 

 alfalfa, cotton, hops, sugar-beets, and va- 

 rious shrubs, hot-house plants, and shade 

 trees. Up to the time that Dr. Smith 

 undertook his investigations its cause and 

 character were entirely unknown. 



♦Journal American Medical Association; 

 American .\ssociation for Cancer Research; 

 Journal Experimental Medicine. 



A NEW BACILLUS FOUND 



He has proved the parasitic nature of 

 this disease (Bulletin 213), and now 

 states (Bulletin 255) that it is nothing 

 more or less than a plant cancer, since it 

 is due to parasitic stimulation going on 

 within the cells and leading to abnormal 

 proliferations essentially like those pres- 

 ent in cancer of men and animals. 



While Dr. Smith has surrounded his 

 conclusions with all those qualifications 

 so dear to the modesty of the scientist, 

 there is no doubt that he has made a dis- 

 covery of the first magnitude in pa- 

 thology, and has indicated a line of re- 

 search which investigators of human 

 cancer will be unable to ignore. 



In 1904 the Department of Agriculture 

 received a number of margurites, or 

 Paris daisy plants, which were infected 

 with gall-like growths on the stems and 

 leaves. They were sent in to the De- 

 partment by one of the large commercial 

 growers in New Jersey, accompanied by 

 the statement that the galls appeared, 

 without apparent cause, both on plants 

 grown in the open in summer and under 

 glass in winter. 



now THE DAISY HELPED 



The first result obtained from the in- 

 vestigations undertaken by Dr. Smith 

 was the establishment of the fact that 

 these growths were not due to insect in- 

 juries. The next step was to discover 

 whether the galls were due to infection 

 by fungous growths, and this was de- 

 cided in the negative after very conclu- 

 sive experiments. The possibility of 

 these growths being due to bacteria next 

 presented itself and was investigated, 

 but for some time the results obtained 

 from the experiments were so inconclu- 

 sive that the bacterial hypothesis was 

 temporarily abandoned. Every eflfort 

 was then made to produce the galls by 

 mechanical injuries practised upon the 

 plants in every stage of growth, but ex- 

 periments in this direction were fruitless. 



More than two years of careful in- 

 vestigation had been consumed before 

 Dr. Smith and his assistants were able, 

 bv bacteriological culture-methods, to iso- 

 late anv organism which would reproduce 

 the disease when plants were inoculated 



