STRUCTURE AND DEVELOPMENT OF BONE. 
125 
in single file. It does not appear that the number of cells entering into the formation 
of a series is at all limited ; hence the lines or columns vary in length. Neither 
does it appear that the consecutive lines are placed, as a rule, end to end, so as to 
form one long continuous straight line by the junction of several shorter ones. On 
the contrary, each series is complete in itself, and is generally placed a little to the 
one or other side of those above and below it. We have in fact interrupted lines of 
cells, each line the offspring of a single cell, the outer walls of which have merged 
into the intercellular or hyaline tissue. 
When the destined number of cells forming a linear series has been developed, 
each cell becomes itself a centre of growth. The granular cell enlarges, together with 
its nucleus, and becomes invested with a cell-wall. In examining a line of these 
bodies extending from the forming bone of the diaphysis, we shall see them in various 
degrees of forwardness. Thus, if attention be directed to the end of the line furthest 
from the bone, the cells will be found small in size, granular, and with a perceptible 
nucleus, but without an outer wall, distinguishable from the hyaline substance, which 
is abundant between the contiguous lines, but small in quantity between the cells 
composing the lines. But if the other end of the line be examined, very different 
conditions will be observed. The granular cells will be seen to have become 
rounded in form, to have increased to three times their original bulk, and to possess 
well-marked circular nuclei; in addition to which each granular cell will have 
acquired a thick pellucid outer wall, while the hyaline tissue between contiguous 
lines of cells will have dwindled down to a thin film, excepting in those parts where 
spaces are necessarily left in the approximation of spherical bodies (Plate VI. figs. 19, 
20). The abundance of the hyaline tissue in the earlier condition of cartilage, affords 
space for the development of the cells in the breadth of the bone, but in the direction 
of the length of the bone we find but little of that tissue, yet each component cell of 
the almost innumerable lines of cells that exist, even in a bone of small size, is itself 
a centre of growth. At the osseous end of a line, a single cell occupies more space 
than four or five at the opposite extremity; and as in each situation the cells are im- 
bedded in hyaline tissue, it is evident that there is a concurrent growth of the latter 
throughout each line of cells, and also of the cells and hyaline tissue in the breadth 
of the cartilage. But for this provision of nature, cells would grow at the cost of 
those in their neighbourhood, a condition which obtains wherever space for a 
secondary development of bone is required, a description of which will follow in 
the subsequent pages of this paper. Then, again, had we concurrent growth in each 
cell of a series without a similar growth in all the other series, throughout the breadth 
of the bone, the growing series would encroach upon the cartilage in which the linear 
arrangement had not commenced, and ultimately unite by osseous tissue the epiphysis 
and diaphysis before the bone had acquired its normal length. And supposing 
concurrent growth to take place over the one-half of the breadth of a bone and not 
in the other, the bone would become curved and the limb distorted. 
MDCCCLIII. 
s 
