94 INDEPENDENT CELLS UNITED 



thus an uninterrupted passage from one cell-cavity into the 

 other is produced. I am not certain as to whether a similar 

 process does not take place in some fibres of the crystalline 

 lens. 



The transformations which the cells undergo are not, how- 

 ever, restricted to those already mentioned. A completely 

 opposite process occurs in the cortical substance of the shaft 

 of feathers, viz. a division of the cells into fibres. By this 

 process, out of a single cell several fibres are generated, which, 

 in the first instance, are united together by the rest of the 

 substance of the cell, but at a later period of development may 

 be insulated to a considerable extent. An elongation of the 

 cells into these fibres takes place, indeed, at the same time, 

 but the major portion of each fibre is formed by the division 

 of the bodies of the cells. 



With respect to the formation of the cells of this class, we 

 find it to be a constant rule, that their size increases in pro- 

 portion with their age, a fact which Henle has already pointed 

 out with regard to the epithelium. We have seen in the dif- 

 ferent tissues, that the nucleus is first present, that the cell is 

 then formed around it, the nucleus, therefore, being the true 

 cytoblast, and that it holds the same position in these cells 

 that it does in those of plants, being fixed eccentrically upon the 

 internal surface of the wall. Cell and nucleus advance in 

 growth for a time, the former, however, much more vigorously 

 than the latter. The nucleus is generally absorbed after the 

 formation of the cell is completed. The generation and growth 

 of the cells and all the phenomena connected with the nucleus 

 resemble those of the vegetable cells, and we may unhesi- 

 tatingly draw a parallel between them. In no class is the 

 quantity of the cytoblastema smaller than in this. In the 

 immature state the walls of the cells lie close together, with 

 at the most, but a minimum of intercellular, substance be- 

 tween them at points where three cells are in contact, and it 

 is only between those nuclei, around which no cells have as yet 

 formed, that a somewhat larger quantity of cytoblastema is 

 present. 



The class of cells now treated of, and the teeth which will 

 be examined in the following class, have been comprised under 

 the term unorganized tissues, and their growth represented as 



