Chapter J 



Organismal Differentials and Specific Adaptation 

 of Tissues and Their Products 



In the preceding chapters we have used the interactions between whole 

 organisms or parts of organisms, between organisms and tissues or 

 organs, as indicators of organismal relationship; which means the rela- 

 tionship of organisms or of parts of organisms, in accordance with the data 

 of phylogeny; and it is the organismal differentials which express these 

 relationships ; but in addition the interaction between certain substances 

 which are produced by organisms, or the interaction of such substances with 

 cells or tissues, may likewise indicate these relationships. If a tissue or such 

 a substance interacts more efficiently with an organ and its products derived 

 from the same phylogenetic group than with an organ or its products derived 

 from a strange phylogenetic group, then these substances or tissues may be 

 designated as "specifically adapted" to each other, especially if the degree of 

 efficiency in this interaction is the greater the nearer the phylogenetic rela- 

 tionship. We have previously discussed various interactions of tissues which 

 are mediated by substances which, as a rule, do not carry the organismal 

 differentials, such as hormones and organizers, the latter functioning as 

 organ- and tissuespecific substances. We also have given some reasons for 

 assuming that certain substances bearing individuality differentials may 

 function as autogenous regulators, which maintain the equilibrium between 

 adjoining tissues ; the localized substitution of a homoiogenous for an autog- 

 enous tissue may alter the normal activity and relationship of tissues, and 

 there are good reasons for believing that these changes are caused by the 

 character of the substances given off by homoiogenous tissues. However, 

 before we enter into a discussion of such substances, in which organismal 

 differentials determine the specific adaptation of tissues to each other, it 

 might be well to define again the different meanings which may be attached 

 to the terms specificity and specific adaptation, as far as they refer to 

 organisms. 



1. The term "specificity" may be applied solely to organs or tissues inter- 

 acting within an organism, without reference to the organism as a whole; 

 such a condition may be designated as organ, tissue or function specificity. 

 The term "specific" may thus accentuate differences between different organs 

 and tissues within the same kind of organisms. It may include the most 

 important organ and tissue differentials, as well as others of secondary 

 importance; and, furthermore, structural and functional peculiarities which 

 depend presumably on the presence of such differential substances. We have 

 discussed these organ and tissue specificities in the preceding chapter. In a 

 wider sense, this term may also include enzymes and hormones produced by 



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