12 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



Not every substance produced by tissues or accumulating in certain organs 

 possesses an individuality differential. Many hormones, and the vitamines, 

 do not have individuality differentials, while other hormones have at least 

 some of the coarser organismal differentials. It is especially the most complex 

 protein substances which act as bearers of organismal differentials. But there 

 are end-products of embryonal differentiation in which the cells, which give 

 origin to certain tissues, have been largely replaced by secondary paraplastic 

 substances, such as the lens fibers of the vertebrate eye. In these the finer 

 organismal differentials have apparently disappeared and only some of the 

 coarser ones have remained; instead, the organ differentials have become 

 more prominent. This is indicated if serological tests are used. However, if we 

 use finer tissue reactions as a test, the presence of individuality differentials 

 can be demonstrated even in tissues of this kind, as shown in the recent 

 experiments of H. T. Blumenthal. He has demonstrated that after homoio- 

 transplantation of a lobe of thyroid gland, and of pieces of liver or kidney, 

 from guinea pigs to other non-related guinea pigs, the number of lymphocytes 

 circulating in the blood rises, about five to seven days after transplantation, 

 by approximately 15 to 25 percent, and having reached this maximum it 

 begins to fall again. After transplantation of cartilage however, such a rise 

 is lacking entirely or almost entirely, because the amount of homoiodifferential 

 given off by this tissue is apparently insufficient to reach the threshold neces- 

 sary for the reaction. After syngenesiotransplantation the increase in lympho- 

 cytes begins, on the average, at a later date and remains lower. After hetero- 

 transplantation it is the polymorphonuclear leucocytes which show an increase 

 in the general circulation ; later they fall to the normal level and this phase is 

 followed by a second phase in which the lymphocytes rise ; after a few days 

 this latter rise is likewise followed by a fall. As far as we can judge, these 

 changes in the number and character of the blood cells are specific; inert 

 foreign bodies, for instance agar, do not bring about such a rise. The effects 

 produced by transplants on the lymphocytes and polymorphonuclear leuco- 

 cytes circulating in the blood are closely parallel to the effects which the trans- 

 plants exert locally on the lymphocytes and polymorphonuclear leucocytes, but 

 some of the effects of the strange organismal differentials are more readily 

 demonstrated by a study of the cell and tissue reaction taking place around 

 the grafts. By means of this general reaction it can be shown that the lens of the 

 eye also possesses an individuality differential, although, if serological tests are 

 used, it seems to be devoid of species and individuality differentials. 



We see, then, that tissues give off substances which differ in their effects in 

 accordance with the genetic relationship of the tissues to the host organism. In 

 their own natural habitat these substances are of an autogenous character and 

 do not incite any abnormal reaction; but in accordance with the genetic 

 strangeness existing between transplant and host, they assume the character 

 of toxic substances, which call forth abnormal reactions in the host. In near 

 relatives these substances — the organismal differentials — act as syngenesio- 

 toxins ; in a strange individual of the same species they act as homoiotoxins, 



