CELL-GROWTH. 667 



these canals are named pore-canals (fig. 300, No. 6). 

 They do not perforate the outer layers ; consequently the 

 blind ends seen through the outer membrane, and whicli 

 were supposed to be aj)ertures, are nothing of the kind. 

 Henle believes he has found canals in cells in animals 

 similar to those in vegetables — in the cartilage of the 

 epiglottis, for instance. In other instances, 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. 300, jSTo. 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. 300, 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 fi.bre. 



Development of Comj^licated 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. 300, Nos. 13 and 14). 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 said to be formed. 



Action of Cells. — The subsequent changes of the cell 

 depend in a great degree on endosmosis, or diffusion. The 

 nature of the membrane is a necessarv condition, for it 



