Chapter 6 



Organ (Tissue) Differentials and Their Analysis 



by Serological Methods 



We have discussed the difference existing between the organismal 

 differentials and the mosaic characters which compose the indi- 

 vidual. It is the latter with which Mendelian heredity and also 

 embryology have so far been almost exclusively concerned. The organismal 

 differentials are common to all parts of an individual, except perhaps certain 

 paraplastic structures ; they thus differ from the mosaic characters which 

 distinguish the various organs and tissues in the same individual, and which 

 are about the same in organs and tissues of the same type in two different 

 individuals with distinct individuality differentials. As we have seen, it is 

 possible to analyze the organismal differentials not only by means of trans- 

 plantation but also by means of serological experiments, one of these two 

 methods being preferable in certain ranges of the spectrum of relationship, 

 the other in other ranges. Similarly, it is possible to analyze by serological 

 methods the organ differentials, those chemical factors which are the same 

 in analogous organs in different individuals, but which differ in the different 

 organs within the same individual. Moreover, it has been found that there 

 are a few organs or tissues in which, under certain conditions of experi- 

 mentation, species differentials cannot be demonstrated by serological meth- 

 ods, but in which organ differentials can be distinguished by these means. 

 The first example of this kind observed and the one best known is the lens 

 of the eye. Uhlenhuth found that this organ can function as antigen and 

 lead to the production of anti-sera, which, however, react about equally 

 against the lens substance of mammals, birds, reptiles and amphibia, while 

 they do not affect other organs of the species whose lens was used for 

 immunization. 



Organ differentials are, therefore, factors inherent in organs or tissues; 

 they are very similar in the corresponding organs and tissues of different 

 individuals and species and represent the structural and functional char- 

 acteristics of these organs and tissues, while the organismal differentials are 

 the substances which distinguish organisms as such from one another, and 

 are the same in different organs and tissues of the same individual. The 

 organ differentials represent what is different and distinct in different parts 

 of the same organism, while the organismal differentials represent what is 

 common to different parts of the same organism but differs in analogous 

 organs and tissues of different individuals and species. 



Potentially, both organismal and organ differentials are present in the 

 fertilized egg in the form of precursor substances. These differentials are in 



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