44 MULTIPLICATION AND NEW PRODUCTION OF CELLS. 



around it a portion of the contents of the cell ; so that the 

 cell-wall, which is at first merely doubled inwards by a sort 

 of hour-glass contraction, at last forms a complete partition 

 between the two halves of the original cavity. The process 

 may be repeated either in the same or in a transverse direc- 

 tion, so as to produce four cells, which may be either arranged 

 in a single line o o o o or may form a cluster gg ; and 

 another subdivision of each cell will, of course, again double 

 the entire number. In other cases, however, the nucleus 

 appears to break up at once into several fragments, each of 

 which may draw around it a portion of the contents of the 

 parent- cell, which becomes invested by a cell-wall of its own ; 

 and thus the cavity of the parent-cell may at once become 

 filled with a whole brood of young cells, without any successive 

 subdivision. Generally speaking, the former method seems 

 to prevail in structures which, like Cartilage, have a com- 

 paratively permanent destination ; whilst the latter is followed 

 in cases in which the cells thus formed are destined only 

 for a transitory existence. This is the case especially in Can- 

 cerous structures, which are particularly distinguished by 

 their proneness to the rapid production of cells within cells. 



34. The production of new cells in the midst of an or- 

 ganizable blastema or formative fluid, such as is poured out 

 from the blood for the reparation of an injury, is a very 

 different process. This blastema, when first effused, is an 

 apparently homogeneous semi-fluid substance ; as it solidifies, 

 however, it becomes dimly shaded by minute dots, and as it 

 is acquiring further consistence, some of these dots seem to 

 aggregate, so as to form little round or oval clusters, bearing 

 a strong resemblance to cell-nuclei. These bodies appear to 

 be the centres of the further changes which take place in the 

 blastema ; for if it be about to undergo development into a 

 fibrous tissue ( 18), they seem to be the centres from which 

 the fibrillation spreads ; whilst, if a cellular structure is to be 

 generated, it is from them that the cells take their origin. 

 The first stage of the latter process appears to consist in the 

 accumulation of the substance which the cell is to include, 

 about each nucleus, and around this the cell-membrane is 

 subsequently developed. It is in this mode that the de- 

 velopment of new structures, for the filling up of losses of 

 substance, is provided for; and it appears, from recent 



