576 Crown Gall-Animal Cancer Analogy 



Itchikawa's results. It had been said that the incentive for their 

 experiments had been the parasitic action on rats obtained by 

 Fibiger when he fed rats witii nematodes taken from muscles and 

 the thorax of roaches. Fibiger also made a series of coal-tar 

 paintings on white mice, and in 1921 his results as well as those 

 of Deelman of the Leeuwenhoek laboratory of Amsterdam and 

 some English experiments by Murray and Woglom were an- 

 nounced. Smith described still other experiments from England 

 and Denmark. 



His purpose in the study of tar cancer experiments was to 

 strengthen his crown gall analogy. In March 1923, after reading 

 Dr. Deelman's recent paper on tar cancer in mice, he called Dr. 

 CuUen's as well as Dr. Bloodgood's attention to the article. In 

 his letter to Dr. CuUen he underscored Deelman's finding that in 

 the youngest tar cancers a horizontal growth "' in all directions 

 by cancerous conversion of neighboring cells " takes place plus 

 an invasive growth, and attached special significance to tiie Dutch 

 pathologist's view that " the cells are hypertrophied before they 

 become cancer cells." The disclosures were believed to " throw 

 much light on the origin of cancer." 



In his address on twentieth-century cancer research,^-^ Smith 

 predicted that great advances would result from the use of " coal 

 tar distillates " and " soot extracts." Since then, from the coal 

 tar, carcinogenic hydrocarbons have been derived, and from the 

 coal tar hydrocarbons extracts and by-products. He illustrated his 

 point by examples. One was: 



Recently an attempt has been made by Bloch and Dreifuss (Sch. Med. 

 Wochenschr. Nov. 10, 1921) to isolate the active principle from coal tar 

 and these efforts if we may believe the preliminary report have proved 

 remarkably successful and will greatly advance our knowledge. They 

 began work in 1920 using rabbits, with the same results as Yamagiwa 

 (number not stated) ; guinea pigs, which proved resistant; and white mice 

 which yielded results "exceeding anything hitherto obtained." Raw tar 

 was used only on a small part of the animals. All the fine results were 

 obtained with a definite fraction of the coal tar, produced by distillation. 

 Corresponding to English observations on the variable number of cancers 

 in men who handle various kinds of coal tar products (H. C. Ross, J. 

 Cancer Research, 1918) the bases, phenols and hydrocarbons, which come 

 over at low temperatures, were found to be negligible. With the first two 



^"0/>. cit., 313-314. 



