534 THE MICROSCOPE. 



solid plate or cell in a rudimentary state. The first kind 

 is seen in cartilage ; here the walls of the cell become in- 

 creased in thickness and coalesce with each other, mixing 

 at the same time with the intercellular substance, while 

 the cavities or vacuolce remain distinct, but are rendered 

 smaller by this process of deposition. In the second kind, 

 cells coalesce, but their cavities or vacuolce run into each 

 other: the tubules of some glands are thus formed. (Fig. 

 269, No. 8.) Where the cells touch they coalesce, and 

 the thin walls dissolving, a single elongated cavity is formed. 

 Another mode is, the cells may be aggregated, like a 

 bunch of raisins, and the parts in contact with each other 

 disappear, so constituting a multilocular cavity : examples 

 of this are seen in the racemose glands. (Fig. 269. No. 

 9.) Schwann conjectures another mode of coalescence. 

 From cells formed as usual, processes sprout out ; but this 

 change takes place at the expense of the cell-membrane 

 itself, and when it has gone on to some extent, we have 

 the appearance of a net-work formed. (Fig. 269, No. 

 11, and 12.) Capillary vessels are formed in this way. 

 Cells, we thus perceive, coalesce to form tissues, when 

 they have not attained their full growth as such ; or when 

 they have been fully formed they become flattened, and 

 assume the solid form. Deposits of matter may take 

 place from the cytoblastema with similar adjoining sub- 

 stance, constituting a delicate membrane, with here and 

 there nuclei, as in the capsule of the lens, the membrane 

 of the aqueous humour of the eye, or sheath of the primi- 

 tive fasciculus of muscle ; or the cells may coalesce in the 

 linear series, to form fibre. 



Development of Complicated Cells. Here the nucleated 

 cell is surrounded by a deposit, and that again surrounded 

 so as to constitute a membrane ; so that the nucleated cell 

 may be looked upon as the nucleus to the cell so formed. 

 (Fig, 269, Nos. 14 and 13.) Sometimes the nucleus under- 

 goes important changes in the development of tissues, as well 

 as the cell itself. In some cases, where the cells have 

 joined in the linear series, the nucleus becomes oval, elon- 

 gated, so that the nucleus of one cell tends to meet the 

 nucleus of another cell; they subsequently coalesce, and 

 thus fibre is formed. That so-constituted filament differs 



