532 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



the present lack of satisfactory serological methods for the detection of these 

 organ or tissue differentials. 



The organ differentials develop in the embryo and undergo a predetermined 

 sequence of transformations. As a rule, the organismal differentials, or their 

 precursors, are present in the developing organs and tissues ; however, certain 

 endproducts of these transformations of organ-forming substances may lose 

 a part, or even all, of their organismal specificity, as occurs for instance in 

 the case of some enzymes and many hormones and related substances. Also, 

 the endproducts of tissue differentiation, such as keratin and lens fibers, may 

 lose entirely or in part the finer organismal differentials, while the organ 

 differentials retain their full strength ; this applies only when certain serologi- 

 cal tests are used as indicators for the organismal differentials. Because of 

 the relative predominance of the organ differentials and the diminution in 

 the significance of the organismal differentials in certain organs or tissues, 

 it is possible to demonstrate by serological tests, organ specificity against 

 tissues and substances derived from the same species when it is difficult to 

 demonstrate individuality and species differentials. Homoiogenous lens, 

 spermatozoa, keratin, thyreoglobulin, fibrinogen, and even insulin, may 

 function thus as organ, tissue or substance antigens. Likewise casein from 

 goats' milk and the albumin of chicken egg may serve as such antigens in 

 goats and chickens, respectively. In a similar way, Schwentker and Rivers 

 produced antibodies against rabbit brains in rabbits, not only by the use of a 

 combination of rabbit brain extract and pig serum, but also autolyzed or other- 

 wise pathologically altered brain as such could serve as antigen. Substances 

 of a homoiogenous nature may function in serological tests as antigens if 

 they are abnormal or if they do not occur in the circulation under ordinary 

 circumstances. 



Both organismal and organ differentials develop thus by a chemical epi- 

 genesis in the course of phylogenetic and ontogenetic development. However, 

 while the organ differentials or their precursors not only undergo very far- 

 going, specific changes during embryonal development, but are also readily 

 accessible to experimental modifications, the organismal differentials or their 

 precursors seem to be fixed; so far it has not been possible by experimental 

 means to transform one organismal differential into another, at least in 

 higher organisms, while it has been possible to change, experimentally, the 

 mode of development and the transformations of organs and tissues. 



We are here concerned only with the serological methods employed for 

 the analysis of organ differentials. As to the criteria that can be used for 

 this purpose, we assume the presence of organ differentials, in contrast to 

 organismal differentials, under the following conditions: 



(1) If an immune serum, e.g., one against fowl egg, differs in its reaction 

 qualitatively or quantitatively from one against blood serum of fowl, or 

 against other organs, tissues or substances derived from the same individual 

 or species, we conclude that an organ differential was involved in the 

 antigenic action which gave rise to the formation of the immune serum. The 



