130 MUSCLE, 
the cell-walls then become blended, in such manner that 
merely simple septa remain, dividing each succeeding cell-cavity 
from its neighbour. These septa, however, become absorbed, 
so that the cavities of the different cells communicate. Instead 
of a number of primary cells, we then have one single long 
one, which we shall call a secondary cell. The cavity of such 
a one, therefore, consists of the united cavities of the original 
cells, and its cell-membrane of all their blended cell-mem- 
branes, except that the parts with which they were in contact 
are absorbed. The growth of the secondary cell proceeds 
like that of any simple imdependent cell. This appears to 
be the process of formation in muscle and nerve, so far, at 
least, as the observations, which will presently be communi- 
cated, extend. When the primary cells have a stellate figure, 
their bodies are not applied in rows, as in nerve and muscle, 
but are generated in larger imterspaces filled with cytoblas- 
tema or with cells of another kind. Their prolongations, 
however, come in contact, the walls coalesce at the points 
of junction, and the blended septa then become absorbed, so 
that the cell-cavities, which were at first separated, now com- 
municate. In this manner, when several prolongations of 
one cell come into contact with those of another, or of several 
others, we obtain, in the place of isolated, hollow, stellate cells, 
a network of canals, which are, in the first instance, somewhat 
thicker at the parts corresponding to the bodies of the cells, 
but become of pretty equal dimensions, in consequence of 
more vigorous expansion of the communicating prolongations. 
This appears to be the mode in which the capillary vessels are 
formed. The followmg detailed statement of observations 
upon the relation which muscles, nerves, and capillary vessels 
bear to elementary cells, will show how far the description 
just given, as the probable mode of formation, is to be regarded 
as proved by these, as yet, very incomplete researches, and will 
also indicate what deficiencies have yet to be supplied. 
1. Muscle. To ascertain the relation which this tissue 
bears to the elementary cells, we must have recourse to the 
history of its development. I was, unfortunately, prevented 
from investigating the earliest formation of muscular fibre, in 
consequence of not being able to obtain any very young 
