PRACTICE OF MEDICINE AND HYGIENE 



necessity of repeating the experiments. It has 

 been found that cancer can be cultivated best 

 in rats and mice. The line of research now 

 proving most hopeful is in the production of 

 artificial immunity in infected animals. This 

 has been accomplished. It now remains to ap- 

 ply these principles to man. As one observes 

 what can be done with these animals in render- 

 ing them immune to cancer he can not but 

 think that we are nearer the long sought secret 

 than ever before, and that cancer is to take its 

 place among the conquered diseases. 



Although this line of research has been in 

 progress only since 1902, brilliant results have 

 been secured. It has been learned that cancer, 

 unlike the infectious diseases, is extremely sen- 

 sitive to constitutional conditions. Reinocula- 

 tion increases the virulence of the growth. By 

 vaccinating animals with certain slowly growing 

 tumors an immunity has been secured even 

 against the most virulent cancer. Immunity 

 has also been produced by injecting the ani- 

 mals with extracts from certain normal organs. 

 In dogs a number of cases have been cured 

 by transfusing into the circulation the blood of 

 dogs previously rendered immune. A number 

 of the best trained scientists in the world are 



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