Physiological Basis of Restitution of Lost Parts 491 



some way to the normal functioning of the others, and dependent 

 to the extent that the removal of one part may alter only to a cer- 

 tain degree the quality and quantity of the activity of the surround- 

 ing parts, without producing extensive modification of structure 

 or function" (Holmes '07, pp. 426, 427). 



The first part of this argument seems to me to obscure the real 

 point at issue. If the relation between A on the one hand and 

 B-F on the other is not at least largely one-sided, removal of A 

 must alter B-F, and if, as Holmes assumes, the new tissue which 

 replaces A is more dependent on B-F than they on it, it becomes 

 still more difficult to understand how the new tissue can replace 

 y/, for, so far as B-F are concerned, it does not at first take the 

 place of A functionally. In the last sentence quoted. Holmes 

 attempts to save his symbiotic theory after admitting that in regen- 

 eration the relation may be more or less one-sided, by suggesting 

 the existence of symbiotic relations which do not produce "exten- 

 sive modifications of structure or function" when one part is 

 removed. It seems to me that such relations are negligible quan- 

 tities so far as form-regulation is concerned, for if removal of a 

 part of the complex does not produce extensive modifications of 

 structure or function in the parts remaining, we must certainly 

 conclude that the presence of this part is not essential for the main- 

 tenance of the characteristic structure and function in the other 

 parts. Evidently then this assumption does not relieve us from 

 the necessity of assuming that the remaining parts are, so far as 

 form and structure are concerned, practically independent of the 

 part removed, i. e., that the relations involved in form-regulation 

 are largely one-sided in cases where restoration of the missing part 

 occurs. It makes no diff'erence whether we regard the persist- 

 ence of B-F in essentially unchanged condition after the removal 

 of A as due to "relative stability" or to real independence of ^. 

 The fact remains that A can be restored only in case the other 

 parts do persist essentially unchanged during the period between 

 its removal and its restoration to a certain stage of development. 

 And it is just as certain that Holmes' symbiotic hypothesis cannot 

 account for such persistence except by assuming the existence of 

 special conditions which modify the relations between parts so 



