422 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



tumors, and this seems to be the case ; it likewise has been found impossible to 

 immunize against a tumor with autogenous tissue. However, there is an ex- 

 periment by Murphy which does not seem in accordance with this interpreta- 

 tion. He found it possible to prevent the growth of autogenous carcinoma 

 transplants by the local application of erythema-producing X-ray doses to the 

 skin ; but in this case we have probably to deal not with an effect on the lympho- 

 cytes but with a condition of a different nature. Through radiation the tissue 

 has presumably been made into an unfavorable soil for the development of 

 the graft. The incorporation of the latter into the host and its nourishment 

 are inhibited under these circumstances, which are non-specific and would 

 therefore affect tissues, irrespective of their relationship to the host. 



However, lymphocytes are attracted not only locally to a tumor possessing 

 a strange individuality differential, but they are increased also in the general 

 circulation, due to the fact that the homoiodifferentials enter also the blood 

 vessels and various organs. This is another instance of the resemblance of 

 tumors to normal tissues possessing a strong individuality differential. But no 

 proof has been given for the view that it is on account of these lymphocytic 

 changes in the whole organism that immunity develops. The production of 

 antibodies probably depends on the stimulation of the reticulo-endothelial 

 tissue. 



The great similarity in the behavior of lymphocytes after transplantation of 

 tumors and of normal tissues, and the significance of the relations of the 

 organismal differentials of host and transplant in determining the nature and 

 intensity of these reactions, has been further confirmed by the recent investi- 

 gations of Blumenthal, concerning the alterations which take place in the 

 blood cells of animals into which pieces of tumors have been transplanted. 

 There is a complete analogy between such alterations and those which occur 

 after transplantation of normal tissues ; differences which do exist are due to 

 secondary conditions. Homoiotransplantation of rat carcinoma and sarcoma 

 into rats brings about an increase in lymphocytes in the blood, which begins 

 on the fourth or fifth day following transplantation and persists for eight to 

 ten days, or sometimes longer, the maximum being reached between the 

 seventh and ninth days. Quantitatively, the reaction is of about the same order 

 as the one following transplantation of homoiogenous normal tissues, and it 

 may occur whether the tumor grows or not. The same results were obtained 

 in mice after homoiotransplantation of tumors, either into the same inbred 

 strain or into strange strains. In these two types of transplantation the 

 changes in the blood were similar, although the tumors grew in the same 

 strain, while they did not grow in strange animals. Still, the increase in the 

 number of lymphocytes in the first type was not quite as rapid as that in the 

 second type, although it tended to persist for a somewhat longer period; in 

 transplantations between different strains, the curve representing the variations 

 in the lymphocyte counts showed a steeper ascent as well as a steeper descent. 



Homoiotransplantation of a benign rat tumor, an adenofibroma of the 

 mammary gland, likewise caused an increase in lymphocytes, but it was a little 

 lower than that observed after transplantation of cancerous tissues and there 



