414 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



is even less than the usual concomitant immunity and the degree of resistance 

 following extirpation of mouse carcinoma IX. (f) Considering the relative 

 weakness of the immunity obtained by inoculation of normal tissue, it might 

 be foreseen that this type of immunization is ineffective against a tumor 

 possessing a great growth energy, or one as resistant to injurious conditions 

 as the chondroma of Ehrlich. Rous and Murphy were not able, therefore, 

 to produce immunity by inoculation of normal tissues against the Rous 

 chicken sarcoma, although during retrogression of these tumors there devel- 

 oped spontaneously an immunity which seemed to be directly against the 

 agent. 



(5) The demonstration of immune substances in the body fluids or tissue 

 extracts of animals which have been inoculated with cancerous material or 

 in which cancer has grown. 



In the blood of an animal which has become immune against certain 

 bacteria, either by recovering from the disease caused by them or by vaccina- 

 tion with the microorganisms or certain parts of them, the presence or anti- 

 bodies directed against these bacteria can in many cases be demonstrated. 

 Similarly, antibodies have been produced against proteins and against cells 

 belonging to a different species, and in some instances even against certain 

 cells belonging to the same species but to different individuals, or against 

 certain kinds of tissues and organs characteristic of a species. It is natural 

 that following the proof that an active immunity can be produced against 

 transplanted tumors, the question should have been raised as to whether there 

 are indications in this case, also, of the presence of antibodies circulating 

 in the blood or retained in the tissues. The existence of such antibodies against 

 heterogenous tumors can be shown, but it has been impossible, at least until 

 more recently, to demonstrate antibodies which developed against homoioge- 

 nous tumors. 



In the large majority of cases, attempts to reveal the presence of antibodies 

 in the blood of immune animals directly, by injecting such blood into sus- 

 ceptible animals of the same species and thereby inhibiting the growth of a 

 tumor graft, did not succeed, although a few investigators (Clowes, Beebe 

 and Gay lord, and C. Lewin) have reported positive results. In subsequent 

 experiments, Lumsden believed he had obtained some positive results by 

 injecting serum of heterogenous animals, immunized against a tumor, into 

 the tumor itself growing in homoiogenous animals, but under conditions 

 which were not favorable to a rapid proliferation of the cancerous tissue. 



By the use of in vitro cultures of tumor cells, Lambert and Hanes found 

 antibodies against cancer cells in the serum of heterogenous, but not of 

 homoiogenous, animals immunized against this tumor. Likewise, Yamagiwa 

 believed he had demonstrated antibodies against mouse tumors in the extract 

 of spleen of rabbits immunized against such tumors. Also, in experiments of 

 Tyzzer there was some indication of an immune substance in the serum of 

 hybrid F 2 , F 3 , and F 4 mice, between Japanese susceptible and white mice 

 non-susceptible to a tumor which had originated in a Japanese mouse. The 

 hybrids were non-susceptible to this tumor. If a piece of this tumor was 



