ORGAN (TISSUE) DIFFERENTIALS 545 



the fact that in the egg yolk reserve substances are involved, in which species 

 differences have developed apparently independently of the general organismal 

 differentials. A similar reservation should, perhaps, be made also in regard 

 to the other instances cited by us, in which organismal differentials seemed 

 to be associated with the organ differentials. The possibility cannot be 

 excluded that there are present in various organs, species-specific substances 

 which, to a certain extent, are graded according to relationship, but which 

 need not be identical with the ordinary organismal differentials. Just as the 

 structures of organs show certain gradations which agree with relationships, 

 so there may perhaps be present in these organs substances and also structures 

 of a particular kind corresponding to this specificity. They would represent 

 secondary or accessory organismal differentials; while the organismal dif- 

 ferentials, which can be recognized by transplantation and especially by the 

 cellular reactions against the transplants, would be the basic, primary 

 organismal differentials. Inasmuch as it is not possible in many cases to 

 apply transplantation tests for the differentiation of these types of organismal 

 differentials, it must be stated again that the term "organismal differentials" 

 is used here, and also in some other chapters, in a more general sense, as 

 representing substances which are gradegl in accordance with the phylogenetic 

 relationship of the organisms from which they are derived, and that there 

 are among these organismal differentials, in the wider sense, the primary 

 organismal differentials, which are characterized by their presence in all the 

 tissues and organs of an organism ; the most characteristic constituent of the 

 latter type of organismal differentials is the individuality differential, which 

 occurs in all or almost all of the tissues and organs of an individual, and 

 which differentiates the individual from all the other individuals of the same 

 species. 



In the case of the proteins of the egg white, Hektoen and Cole have shown 

 that of the five proteins of the white of hen's egg, four are quite distinct from 

 the proteins of chicken plasma and only the conalbumin of the egg seems to 

 be identical with serum albumin. A common immune reaction between egg 

 white and blood plasma of chicken depends therefore upon the admixture of 

 a protein which is identical in both. On the other hand, there exists a 

 pronounced species-specificity of the egg-albumins of various species, and 

 the crystallized egg-albumins of such nearly related species as chicken and 

 duck are immunologically not identical (Dakin and Dale). Of course, in the 

 egg yolk and egg white we have to deal not with substances representing the 

 embryonal precursors of the organismal differentials, but with auxiliary 

 substances surrounding the embryo or serving as food for it. It might there- 

 fore be expected that they are chemically and immunologically distinct from 

 the essential constituents of the developing or adult organisms ; they repre- 

 sent paraplastic substances which are formed in the adult animal. 



We see then, that as a rule substances or cells which contain organ 

 differentials also contain organismal differentials, but that the proportion in 

 which these two differentials are present in the same substance or cell differs 

 in different cases. It seems furthermore that in certain instances organ and 



