CHAPTER V 



THE RANGE OF DOMINANCE, PHYSIOLOGICAL 



ISOLATION, AND EXPERIMENTAL 



REPRODUCTION 



If the conception of physiological dominance which 

 is presented in chap, ii is correct, the existence of a 

 transmission-decrement in the impulses, stimuli, or excita- 

 tions which are the effective agents in dominance must 

 determine a certain range of dominance and therefore 

 a physiological size limit or limit of length for each axis, 

 which cannot be exceeded without physiological isola- 

 tion of the part that lies beyond the range of domi- 

 nance. Moreover, the limit of dominance in a given case 

 must vary with the metabolic rate in the dominant 

 region and the conductivity along the path of trans- 

 mission. Its effectiveness upon a subordinate part may 

 also depend upon the receptivity of the part to the 

 transmitted excitations, and this may be determined 

 by local conditions to which the part is subjected. If 

 the characteristic gradients are present or arise in a 

 physiologically isolated part, such a part may become 

 a new complete individual, if it is not so highly special- 

 ized or differentiated as to be incapable of reacting to the 

 altered conditions by dedifferentiation and redevelop- 

 ment. Some of the evidence bearing upon these aspects 

 of the problem of dominance is considered in this 

 chapter. 



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