TWENTY-FIVE YEARS OF BACTERIOLOGY 141 



against the implanted cancer cells, throw no real light 

 upon the series of events underlying the origin of cancer. 

 The light referred to was shed by the studies of Rous, of 

 the Rockefeller Institute, upon a sarcoma, or fleshy can- 

 cer, of the domestic fowl. This cancer, which arises at 

 times spontaneously in fowl, is subject to successful im- 

 plantation in other fowl. The specificity is accurate ; it 

 will not grow in other birds and grows best in the variety 

 of fowl in an individual of which it originally appeared. 

 Its growth is first local, as is cancer in man, and later 

 metastatic, or, appearing at a distance and starting from 

 microscopic masses of cells derived from the original 

 tumor and carried by the circulation to remote parts of 

 the body. The altogether new and unprecedented fact 

 about this tumor, which has, however, not yet been found 

 to be true of the cancers of mammals, is that it may be 

 induced by the injection into the susceptible variety of 

 fowls, of a cell-free filtered extract of the tumor. In 

 other words, Rous has accomplished for this tumor what 

 bacteriologists had effected for a certain refractory group 

 of the infectious and communicable diseases, namely, re- 

 lating it to a form of life not imagined by the founders 

 of bacteriology, but which their discoveries in the field of 

 the living microscopic, as opposed to the ultramicroscopic, 

 universe brought within range of recent biological re- 

 search. 



SPIROCHETES 



The vicissitudes of bacteriological science, like those of 

 other sciences, have depended upon time and method, and 

 sometimes the one and sometimes the other has served to 

 promote discovery. When by a happy conjunction of 

 circumstances, time and method happen to conjoin, then 

 advances almost startling in nature may take place. 



It is in this way that we may view the remarkable prog- 

 ress of events in connection with a class of special micro- 



