444 SMITH— MECHANISM OF OVERGROWTH IN PLANTS. 



done under the idea that tumors are due to the existence of specific 

 overgrowth stimuh; (b) because done with substances which could 

 by no possibility be conceived to be the product of parasites; and 

 still more (c) because the experiments fell on stony ground, that 

 is into the unreceptive minds of a generation of pathologists pre- 

 occupied with quite other ideas and generalizations respecting tumor 

 growth. 



I refer more particularly to Dr. Hermann von Schrenk's papers 

 (1903 and 1905) on intumescences in cauliflower plants due to 

 copper salts.* and to Dr. Bernhard Fischer's paper on overgrowths 

 of epithelium due to the injection of scarlet red and indophenol into 

 rabbit's ears.^ 



Fischer's paper in particular pointed the way clearly toward 

 the solution of the cancer problem, but it was received very coldly 

 and he became discouraged, and no one else took up the suggested 

 clue. 



What Fischer obtained was downgrowths of epithelium into 

 the connective tissue, strikingly suggestive of epithelioma, but, be- 

 cause these invading epithelial cells subsequently ceased to grow, 

 with disappearance of the stimulus, and were finally absorbed, 

 as one might reasonably have predicted would be the case, they 

 were held to throw no light on the cancer problem ; but if spec- 

 ialists had then assumed that quite other substances than scarlet 

 red and indophenol can cause overgrowths, as we now know, and 

 that some of the substances may be the products of the tumor-pro- 

 ducing parasites, as also we now know, how suddenly luminous the 

 whole subject would have become and what an incentive it would 

 have given, and still gives, to further research ! 



•* See especially Report of Missouri Botanical Garden, 1905, p. 125. 

 ■' Muenchner med. Wochenschrift, 1906, p. 2041. 



