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THE AMEBIC AN NATURALIST 



[Vol. XLIX 



are now the bearers of the tumors. It is therefore neces- 

 sary to conclude that the tumor cells used for transplanta- 

 tion are in this case the sole bearers of the immunity, and 

 that the tumor cells themselves have been actively immu- 

 nized. From the latter experiments we may furthermore 

 conclude that the immunity acquired by tumor cells is 

 transferred to the following generations of tumor cells, 

 and that therefore a hereditary transmission of a char- 

 acter acquired by somatic cells under the influence of 

 external conditions takes place. The conclusion is based 

 on the following consideration : The process of tumor in- 

 oculation consists in the transfer of a very small particle 

 of tumor. Very soon after transplantation most of the 

 transplanted tumor cells become necrotic and only a rela- 

 tively small number of peripheral tumor cells remain 

 alive. These very soon begin to proliferate, and through 

 their proliferation give origin to the developing tumor. 

 If therefore the tumors developing after transplantation 

 in the new hosts are immune, the immunity must have 

 been transmitted from the few cells remaining alive after 

 inoculation to the new cell generations to whom they give 

 origin. A fully developed tumor represents a combina- 

 tion of a large number of generations of tumor cells and it 

 may be assumed that the later generations of tumor cells 

 preponderate numerically very much over the earlier 

 generations. Through how many generations of tumor 

 cells this transmission of the acquired immunity can be 

 propagated remains yet to be determined. From our 

 preliminary experiments, which are, however, not yet 

 definite, it appears not improbable that it extends at least 

 through several series of transplantations. 



Both colloidal copper and hirudin inhibit tumor growth. 

 The sign by which we judge the effect of these substances 

 is therefore essentially the same in both. We might thus 

 be inclined to conclude that their action is identical and 

 that likewise the immunity which they produce, is the 

 same; that animals having received preliminary injections 

 of colloidal copper would therefore be immune not only 

 against the action of colloidal copper but also against 



