THEORIES AND PROBLEMS OF CANCER 233 



against them in a way in which they do not react against the 

 cells of a primary growth. It therefore seems probable that a 

 constituent of the serum destructive to these tumour cells would 

 be more easily produced and would be active to a greater 

 extent and perhaps in a different way from a serum active 

 toward the cells of a primary growth. Indeed, it seems likely 

 that it may be impossible to produce a serum active towards the 

 cells of a primary growth upon these principles. Moreover, it 

 seems very probable that the destructive capacity would only be 

 exhibited towards the particular race of tumour cells which had 

 produced the reaction, in which case it would be practically 

 impossible to apply the method to the human subject, a large 

 quantity of serum being necessary and a sufficient reaction 

 produced only after a number of inoculations of considerable 

 quantities of living cells into the secondary host. The same 

 criticisms apply to the results obtained in producing immunity 

 to subsequent inoculation with the transmissible tumours. 



The experiments in which the rats were inoculated with the 

 cells of the mouse's testis, which afforded striking but less 

 satisfactory results than those in which the serum produced by 

 inoculating with the mouse tumour was used, avoid the sug- 

 gested difficulty with regard to the serum being active against 

 the cells of one particular tumour only. But this method is 

 inapplicable to man on account of the impossibility of obtaining 

 sufficient material from the human subject. Only living cells 

 are effective. In addition there is the insuperable difficulty of 

 obtaining the living cells of the human testis in sufficient 

 quantities and often enough. The cells of the testis do not die 

 immediately upon the death of the individual but practically all 

 are dead in about three hours. 



Many attempts have been made to find chemical compounds 

 capable of exerting a selective action upon cancer cells— that is 

 to say, which will kill the cancer cells without materially in- 

 juring the rest of the body. Wassermann l has recorded the 

 effects produced by a preparation of selenium and eosin upon 

 cancerous tumours produced by inoculation in mice. The 

 preparation was introduced by intravenous injection directly 

 into the circulation and after a number of injections produced a 

 liquefaction of the tumours in the mice which survived the 



1 " Beitrage zum Problem : Geschwiilste von der Blutbahn aus therapeutisch 

 zu beeinflussen," Dcut. in. Woch. December 191 1. 



