REGENERATION IO3 



which control the missing parts which have to be renewed. If 

 therefore we wish to suppose that Bhnnenbach's ' tiisus forina- 

 tivus ' is situated in the idioplasm of the cell, it appears neces- 

 sary to assume that each cell capable of regeneration contains 

 an accessory idioplasm, consisting of the determinants of the 

 parts which can be regenerated by it, in addition to its primary 

 idioplasm. Thus, for instance, the cells in the bone of the upper- 

 arm must contain, in addition to their controlling determinant 2, 

 the determinants 3-35 as accessory idioplasm, which can cause 

 all the bony parts of the fore-arm to be formed anew ; the cells 

 of the radius, again, must contain the determinants 4-20 as acces- 

 sory idioplasm for the reconstruction of the radial portion of the 

 wrist and hand. 



This theoretical illustration may be looked upon, indeed, as 

 representing the phenomena as they occur in reality. It is 

 very possible that the required accessory idioplasm becomes 

 separated from the disintegrating embryonic idioplasm in the 

 earliest stage of development of the entire organ. According 

 to our assumption, the individual determinants are present sitigly 

 in the germ-plasm, and their multiplication increases the further 

 ontogeny advances. As only those determinants which corre- 

 spond to parts to be formed subsequently are required in the 

 accessory idioplasm, the material for the latter is always present ; 

 and we need only assume that in each division of the primary 

 cell of any bone, a portion of the determinants required for the 

 formation of the subsequent parts becomes split off as secondary 

 idioplasm, and remains inactive within the cell until a cause for 

 regeneration arises. 



I shall speak of this group of determinants as accessory idio- 

 plasm (' Neben-Idioplasma""), and its component determinants 

 as siippieinentary determinants (' Ersatz-Determinanten ") . We 

 may imagine that these form a special and minute group en- 

 closed within the id in the neighbourhood of the determinants 

 which control the cell in question. A similar assumption may 

 be made as regards the individual bones of the entire limb. 

 The regeneration of the bisected humerus can be explained by 

 supposing that each cell capable of regeneration possesses an 

 accessory idioplasm, containing the determinants of the cells 

 which will subsequently be formed in a distal direction ; this 

 formation will be possible because the necessary • determinant- 

 material ' is present. The process only depends on the tact that 



