418 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



lymphocytes, an observation which agrees with our findings that polymorpho- 

 nuclear leucocytes tend to collect around heterogenous transplants of normal 

 tissues. Burgess and Tyzzer noted that if the tumor was not destroyed too 

 rapidly through the accumulation of these wandering cells, dense scar-like 

 fibrous tissue was produced in the transplant. Likewise, in a later analysis of 

 these phenomena, Tyzzer (1916) did not interpret these primary cellular 

 reactions as due to and directed against incompatible organismal differentials, 

 which secondarily call forth an immunization, but he adopted Russell's view 

 that natural resistance against tumors is merely the ability of the host to 

 acquire an active immunity against the tumor, while susceptibility means the 

 lack of this ability. Tyzzer assumed, therefore, that in every case the local 

 cellular reaction was due to an active immunity produced against the trans- 

 plant, and it was considered as a phenomenon specific for tumors. 



As to the mechanism underlying this reaction, Tyzzer assumed that in com- 

 bination with an immune body the tumor products become strongly chemo- 

 tatic for leucocytes and at the same time stimulate the surrounding fibro- 

 blastic tissue. In animals already immunized, the reaction not only sets in more 

 promptly, but here also the polymorphonuclear leucocytes are more numerous, 

 while in as yet untreated animals, in which the immunity develops only gradu- 

 ally following the first inoculation, the reaction takes place more slowly and 

 the lymphocytes are found in relatively larger numbers; the preponderance of 

 lymphocytes signifies a milder reaction on the part of the host. In addition to 

 the movements of lymphocytes and polymorphonuclear leucocytes, an increase 

 in the number of fibroblasts occurs in the surrounding tissue, and this he com- 

 pared with the formation of granulation tissue in inflammatory processes. 

 Tyzzer concluded, then, that immunization leads to the production of sensitiz- 

 ing antibodies in the host, and these combine with a substance given off by the 

 tumor to form an injurious substance (anaphylatoxin), which injures the host 

 tissue surrounding the tumor. As a result of such injury, inflammation sets 

 in and lymphocytes, polymorphonuclear leucocytes or monocytes appear. In 

 general, it is the presence of this antigen-antibody combination (anaphyla- 

 toxin) which causes the accumulation of the leucocytes of the host in and 

 around the graft. 



Also, in the case of other tumors cellular reactions around the "transplants 

 were noted and the resistance of the host to transplanted homoiogenous tumors 

 was attributed especially to the lymphocytes. Thus, when chicken sarcoma was 

 transplanted into a naturally immune fowl, Rous and Murphy observed on 

 the fifth day following transplantation the appearance of masses of lympho- 

 cytes around the graft, which then degenerated. In other instances it seemed, 

 however, that the tumor was already seriously injured at an earlier period 

 following transplantation, owing to the failure of the surrounding tissue to 

 provide a stroma for the graft. Similarly, Mottram and Russ, studying im- 

 munity against Jensen rat sarcoma, found that when a piece of tumor was 

 inoculated into non-immunized rats, the lymphocytic reaction which developed 

 around the transplant was very slight and did not seriously interfere with the 

 growth of the tumor. But if, following a first inoculation with experimentally 



