THEORY OF THE CELLS. 10.0 



when no part of the cell is yet formed. Therefore, the greater 

 the attractive force of the cell is, the less concentration of the 

 fluid is required ; while, at the commencement of the forma- 

 tion of a cell, the fluid must be more than concentrated. Bui 

 the conclusion which may be thus directly drawn, as to the 

 attractive power of the cell, may also be verified by observation. 

 Wherever the nutrient fluid is not equally distributed in a 

 tissue, the new cells are formed in that part into which the 

 fluid penetrates first, and where, consequently, it is most con- 

 centrated. Upon this fact, as we have seen, depended the 

 difference between the growth of organized and unorganized 

 tissues (see page 169). And this confirmation of the foregoing 

 conclusion by experience speaks also for the correctness of the 

 reasoning itself. 



The attractive power of the cells operates so as to effect the 

 addition of new molecules in two ways, — first, in layers, and 

 secondly, in such a manner in each layer that the new mole- 

 cules are deposited between those already present. This is 

 only an expression of the fact ; the more simple law, by which 

 several layers are formed and the molecules are not all de- 

 posited between those already present, cannot yet be explained. 

 The formation of layers may be repeated once, twice, or thrice. 

 The growth of the separate layers is regulated by a law, that 

 the deposition of new molecules should be greatest at the part 

 where the nutrient fluid is most concentrated. Hence the 

 outer part particularly becomes condensed into a membrane 

 both in the layer corresponding to the nucleus and in that 

 answering to the cell, because the nutrient fluid penetrates 

 from without, and consequently is more concentrated at the 

 outer than at the inner part of each layer. For the same 

 reason the nucleus grows rapidly, so long as the layer of the 

 cell is not formed around it, but it either stops growing- 

 altogether, or at least grows much more slowly so soon as 

 the cell -layer has surrounded it ; because then the latter 

 receives the nutrient matter first, and, therefore, in a more 

 concentrated form. And hence the cell becomes, in a general 

 sense, much more completely developed, while the nucleus- 

 layer usually remains at a stage of development, in which 

 the cell-layer had been in its earlier period. The addition of 

 new molecules is so arranged that the layers increase more 



