REGENERATION ^ 1 01 



Each of these kinds of cells must he present from the first in a 

 perfectly definite number, and must occupy a perfectl}- definite 

 position. 



Let us follow out this line of reasoning with regard to one 

 system of organs, namely, the bones, and assume for the sake of 

 simplicity that only a single bone-forming cell is present in the 

 first rudiment of the limb. This cell would virtually contain the 

 entire skeleton of the limb ; and w'e should have to attribute to 

 its idioplasm the power not only of giving the succeeding cells 

 of a certain number of generations the character of bone-forming 

 cells, but also of determining the entire sequence of these cells 

 as regards quantity, quality, and mutual arrangement, as well as 

 the rhythm in which the divisions will follow one another. For 

 the particular point at which an interruption occurs in the con- 

 tinuity of the bone, and consequently also the boundary line 

 between two segments of the bony chain, might essentially 

 depend, indeed, on this rhythm. 



We must therefore suppose that the composition of the idio- 

 plasm of the first primordial bone-cell of the limb causes all 

 these sequences to take place : in other words, the idioplasm 

 jfiust contain the deterininants of all the succeeding bone-cells. 

 This may be illustrated by the following diagram (fig. 3), in 

 which the actual processes, which concern hundreds of thousands 

 of cells, are represented as greatly abbreviated, and the ditferent 

 generations of cells are indicated arbitrarily by a genealogical 

 tree, which, however, does not by any means always represent 

 their actual connection. 



Each primary cell of the individual bones is represented in 

 the figure by a circle, and is supposed to be so simple that it 

 can be controlled by one determinant. Thus the primary cell 

 of the entire series of bones is controlled by determinant i, but 

 also contains the determinants 2-35 in its ids. In the first cell- 

 division this cell divides into two, — the primary cells of the upper 

 arm (humerus), and of the fore-arm and hand. The former 

 contains determinant 2, and its further division is indicated by 

 the cells containing determinants 2.a-2x. The latter contains 

 the remaining determinants 3-35, which become separated into 

 smaller and smaller groups in each cell-division, until finally 

 each cell only contains a single determinant. The diagram only 

 represents the main bones of the extremity, — the individual 

 carpals are omitted. 



