36 HEREDITY AND SELECTION IN SOCIOLOGY 



organ possesses a specific activity, a measure of what miglit be 

 called self-assertiveness in relation to other parts.^ In the case 

 of an organ undergoing hjrpertrophy, the loss caused by dis- 

 similation is over-compensated for by the energetic influence of 

 the organ's specific activity. There is a quaUtative regulation 

 of the organ by the organ itself ; in other words, the stimulating 

 and assimilative energies due to the specific activity of an organ 

 can over-compensate for the results of processes of dissimila- 

 tion. From the conception of a specific force in each organ 

 Roux derived his theory of the " struggle between the parts " 

 {Kampf der Teile). For instance, if difierentiated functional 

 stimuli are affecting the embryonic cells of different physio- 

 logical properties. A, B, and C, that cell which is most violently 

 acted upon by the stimulus appropriate to it — we suppose the 

 stimuli A^, B^, C^ to be in appropriate relation to A, B, and C 

 respectively — will increase in development most rapidly. The 

 proportion in which the cells A, B, C will subsequently stand to 

 each other in the finished tissue will depend upon the degree of 

 stimulation which the specific stimuli A^, B^, C^ have respectively 

 exercised. This is what Wilhelm Roux called " the struggle 

 between the parts." 



Applying Roux's suggestion, not to the cells only, but to the 

 component parts of the cell, the determinants, we find that the 

 histological character of a given cell A will be determined by 

 the degree of stimulation which the specific stimuli of the deter- 

 minants within it are capable of exercising. The character of 

 that cell will be determined by a single determinant, and that 

 determinant will be called into action by the preponderance of 

 its specific excitability in relation to the cell. 



Cases where two homologous determinants are present in a 



single cell illustrate still more clearly the results of the action 



of specific excitatory forces. Why, indeed, should one of these 



homologous determinants develop into activity, while the other 



1 W. Roux, Der Kampf der Teile im Organismus. Leipzig, 1881. 



