Piirf "\7" Organismal and Organ Differentials and the 



Specificity of Tissue Reactions 



Chapter I 



The Relative Importance of Substratum and of 



Morphogenic Substances in the Specificity of 



Tissue Reactions, and the Relation of These 



Factors to Organismal Differentials 



IN preceding chapters we have referred to the relations which exist be- 

 tween organismal and organ differentials, and the role which morpho- 

 genic contact substances play in the differentiation of tissues, organs, 

 and in the development of organ differentials. We have also referred to the 

 action of morphogenic substances affecting tissues at a distance from the place 

 of origin of these substances, and to the importance of gene-hormones in the 

 realization of genetic determinations. In this chapter we shall continue this dis- 

 cussion and analyze additional conditions of an analogous kind — some of which 

 are effective also in the adult organism — in which the specificity in structure 

 and function depends upon and also manifests itself in an interaction between 

 hormones and factors inherent in certain tissues. Transplantation of tissues, 

 which act either as carriers of the stimuli or represent the substratum, was 

 used as a method for the analysis of these relationships in a number of in- 

 vestigations. This specificity may, in certain cases, manifest itself also in the 

 differences in the reactions to stimulating or inhibiting factors which are 

 observed when these factors act on the tissues of different individuals, species, 

 orders or classes of animals. We may designate the latter kind of relation as 

 an organismal specificity ; and if this organismal specificity is of such a nature 

 that the stimulating or inhibiting factor originating in a certain individual, 

 species, order or class of animals, is more effective when acting on tissues of 

 the same kind of individual, species, order or class, than when acting on 

 tissues of another kind of organisms, then we have to deal with what may 

 be designated as specific organismal adaptation between the stimulating or 

 inhibiting factor and the recipient tissue. We may therefore distinguish three 

 kinds of specificities: (a) simple organ or tissue specificity; (b) organismal 

 specificity; (c) organismal specific adaptation. 



The problem may arise as to the seat of the specificity of the reactions in 

 such cases, whether it is the hormones and other distance substances or the 

 organs in which they originate, or the tissues on which they act. What factor 

 determines the differences in the behavior of analogous tissues or substances in 

 different individuals, species, orders or classes, or the differences in the behavior 



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