98 THE ACTION OF THE LIVING CELL 



As shown in the protocol, this animal (cat No. 89) 

 withstood periodic injections of cytost for a period of 

 more than two years. During this time several dif- 

 ferent cytost preparations were used, each of which 

 was definitely toxic when injected into the femoral 

 vein of other cats. It follows, therefore, that this 

 animal possessed to a marked degree a natural im- 

 munity to the action of cytost. As this was also en- 

 countered in several other animals the author was led 

 to attempt the production of an artificial immunity to 

 cytost. This interesting aspect of the problem will be 

 discussed later. 



It has been shown previously (Chap. Ill) that cy- 

 tost may be liberated in vivo by agents which bring 

 about cellular destruction and autolysis. If such 

 processes are induced continuously for a protracted 

 period of time, we should expect to obtain results 

 similar to those following the injection of tissue 

 autolysates. Now in vivo autolysis may be accom- 

 plished by a variety of means, such as trauma, burns, 

 and the application of caustic chemicals such as mus- 

 tard oil, ether, chloroform, and alcohol. Of these the 

 last three are most adaptable for prolonged experi- 

 ments, since by regulating the amount injected one 

 may to some degree control the extent of autolysis. 

 Animals which died as a result of such treatment, 

 or were killed after a number of such injections, 

 quite uniformly were found to have suffered the 

 same organic lesions as those injected with ex- 

 tracts of autolyzed tissues. Such observations con- 

 firm the hypothesis that the tissue damage caused 

 by these reagents is responsible for the observed 

 pathology. 



