290 THE PROTEAL TREATMENT OF CANCER 



ceptible that will render it immune to further transplantation. 

 This was done by Ehrlich and his associates by making an orig- 

 inal inoculation with a tumor known to possess a low degree of 

 virulence. Such a tumor being absorbed "spontaneously," it was 

 observed that the animal in which such spontaneous absorption 

 had occurred was now immune against inoculation with tumors 

 of a more virulent type which would almost certainly have grown 

 had not the animal been given added powers of resistance by the 

 original inoculation. 



What is of peculiar importance from the present standpoint is 

 the fact that it was shown presently that inoculation with normal 

 tissue, such as liver, spleen, and blood produced a degree of im- 

 munity comparable to that produced by the inoculation with a 

 mild type of cancer cell. And most interesting of all is the ob- 

 servation of Dr. Levin and others that identical results as to in- 

 duced immunity may be brought about by inoculation with so- 

 called autolyzed tissue, that is to say, with tissue "of which the 

 cells are killed in such a manner as to leave the endo-cellular 

 enzyme-like substance uninjured and active." 



I have quoted Dr. Levin's own phrase as to the use of auto- 

 lyzed tissues, chiefly because it probably expresses the general 

 attitude of mind of experimenters toward this particular aspect 

 of the subject, in that it inferentially ascribes the immunizing 

 influence of the autolyzed tissues to their "enzyme-like substance." 

 It is hardly necessary to tell the reader of the present monograph, 

 however, that in my own opinion the success of the experiment 

 was due not to the presence of any specific enzymes, but to the 

 fact that the tissue used cancer tissue, liver tissue, spleen, blood, 

 or what not had the all-important advantage of being protein- 

 bearing tissue. 



This conclusion, to be sure, is inferential; but I think it will 

 be admitted to find strong support in the fact that all manner of 

 tissues, including even the tissues of an animal of another species 

 (mouse tissues introduced into the rat, for example), can produce 

 seemingly the same condition of immunity. 



Note, now, the very significant fact that when a dog was cured 

 of a transplanted tumor by the transfusion of blood of an im- 

 mune animal in the later experiments made at the Loomis Lab- 

 oratory, it was shown that decompounding and absorption of the 

 tumor itself was an essential part of the immunizing process. 

 This was proved by the fact that it was not found possible to 

 render a dog immune to transplantation of a tumor by transfusing 

 blood before such transplantation. It was only after the tumor 

 had actually been transplanted and begun its growth, that the 

 transfusion sufficed, through the process of destroying the tumor, 

 to give the animal immunity against further inoculation. 



