44 MULTIPLICATION AND NEW PRODUCTION OF CELLS. 
around it a portion of tlie contents of tlie 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 OOOO 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 per man ent 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 
