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MESSRS. J. TOMES AND C. DE MORGAN ON THE 
these bodies granular cartilage cells, as distinguished from a form which the cells 
assume previous to ossification. Cartilage previous to its conversion into bone under- 
goes a rapid growth, which takes place principally in the direction of the long axis 
of the future bone. Each granular cell becomes divided into two by segmentation 
transverse to the line of ossific advance. These are again divided, and the process 
repeated from time to time, till in the place of a single granular cell we have a long 
line of cells extending from the unchanged cartilage to the point where ossification has 
taken place. Contemporaneously with this development of lines of cells, other changes 
are going on in the individual cells composing them. If we examine those situated 
near the advancing bone, it will be observed that the granular cells have enlarged, have 
become separated from each other by wide intervals, and that each has become in- 
vested with a thick pellucid cell-wall (Plate VIII. figs. 19 and 20). The increase in 
the size of the cells has occurred at the expense of the hyaline tissue, which, at those 
points where the rounded cells approach each other, is reduced to a thin film, although 
in the intervals left by the packing of the uncompressed cells it exists to a consider- 
able amount. Here then we have a matrix containing cartilage cells composed of an 
outer pellucid coat, within which is a granular cell containing central nuclei, a cell 
consisting of three distinct parts. The nucleus existed previous to the segmentation 
of the granular cell, but the outer wall is the product of a subsequent development. 
It will be observed that growth is effected by two modes ; first, by the increase of 
the number of the cells ; and, secondly, by the increase of their size individually. 
While these changes are going on for lengthening the shaft of a long bone, cells 
are being added by a somewhat similar process of division to the surface, so as to 
increase the diameter of the cartilage. For the development of the epiphysis the cells 
become multiplied on a similar principle, but instead of occurring in lines they are 
accumulated in oval or rounded groups*. 
From this general view of the subject we will now proceed to consider in detail 
those conditions of cartilage which precede and prepare for its conversion into bone. 
These phenomena may be conveniently examined in the cartilage which connects the 
diaphysis and epiphysis of long bones, and we may take those of a lamb or call, as 
they present the same conditions as are found in the human subject, and have the 
advantage over those of other domestic animals of being readily obtainable at all 
times without the necessity of destroying the animal for the sole purpose of physiolo- 
gical investigation. 
At that point in the cartilage where the linear arrangement of cells commences, 
several of these bodies lie side by side in the same column, but by following the line 
downwards towards the advancing bone, it will be seen that the column usually 
divides, forming two or three distinct lines, in each of which the cells are arranged 
* Previous to the ossification of the epiphysis the cartilage at the heads of the bone is increased in its bulk 
from additions to the surface, by a process somewhat similar to that through which the growth of bone is eflfected. 
This process will be described when the latter subject is considered. 
