STRUCTURE AND DEVELOPMENT OF BONE. 
131 
ceases as we extend our examination towards the bone. Here in the place of cells 
witheiongated processes, or cells arranged in fibre-like lines, we find cells aggregated 
into a mass, and so closely packed as to leave little room for intermediate tissue. 
The cells appear to have increased in size at the cost of the processes which existed 
at an earlier stage of development, and formed a bond of union between them. 
Everywhere about growing bone a careful examination will reveal cells attached to 
its surface, while the surface of the bone itself will present a series of similar bodies 
ossified (Plate IX. figs. 2/, 28 and 29). To these we propose to give the name of 
osteal cells, as distinguished from lacunal and other cells. 
In microscopic characters the osteal cells closely resemble the granular cells of 
temporary cartilage, so closely indeed, that the latter when detached from the car- 
tilage could not well be distinguished from them. They are for the most part sphe- 
rical or oval in form, and lie on the surface of the growing bone in a crowded mass, 
held together by an intervening and apparently structureless matrix (Plate IX. fig. 
2" h). Here and there we find a cell which has accumulated about itself an outer 
investment of transparent tissue, and has in fact become developed into a lacunal 
cell destined to become a lacuna*. These points are illustrated in fig. 29 h. 
The process of growth may be thus described. In the meshes of the fibrous tissue 
* The various views which have heen entertained regarding the formation of the lacunae and canaliculi have 
been concisely stated by Dr. Sharpey, oper. cit. p. 158. He observes, that “ they are generally supposed to be 
derived from the cells of the soft tissue involved in the ossification by some sort of metamorphosis which has 
been variously conceived. Some suppose that the cells become the lacuna and send out branches (like the 
pigment cells) to form the canaliculi (Schwann*)- Others think that it is not the cell but its nucleus that 
undergoes this change, and that the substance of the nucleus is afterwards absorbed, leaving the lacuna (Todd 
and Bowman").” The nucleus described by Todd and Bowman is identical with that which in this communi- 
cation is called the granular cell, and from which the authors have shown the lacuna is formed. “Henle^ 
thinks that the lacuna is a cavity left in the centre of a ceU which has been partially filled up by calcification, 
and that the canaliculi are branched passages, also left in consequence of the unequal deposition of the hard 
matter, as in the instance of the pore cells of plants.” “ It rather appears to me as if the lacunse and canali- 
culi were little varieties left in the tissue during the deposition of the reticular fibres, as open figures are left 
out in the weaving of some artificial fabrics (but not within a cell, as Henle imagined), and that thus the appo- 
sition of the minute apertures existing between the reticulations of the lamellae gives rise to the canaliculi.” “ At 
the same time it seems not unlikely that a cell or a cell-nucleus may originally lie in the lacuna or central cavity, 
and may perhaps determine the place of its formation.” Hassall'* agrees with Schwann, while Gerber^ and 
Bruns“ appear to hold the views of Todd and Bowman. With the exception of Dr. Sharpey, the above- 
named authorities may perhaps dilFer more in the use of terms than in matter of fact. The appearances 
represented in figs. 14 and 27 would at first view seem to justify the opinion expressed by Dr. Sharpey, 
but a careful examination of the tissue during its development, the unquestionable fact that in the development 
from cartilage the granular cell becomes converted into a lacuna, together with the circumstance that lacunal 
cells are frequently found in the Haversian canals and cancellated structure, especially in the hones of old sub- 
jects, and at times imbedded in the structure of the bone, have left no room for doubt in the authors’ minds that 
the lacunse are formed from special nucleated cells, in the manner described in the text. 
' Mikroscopische Untersuchungen. ^ Physiological Anatomy. ® Anatomic Generale. 
* Microscopic Anatomy of the Human Body, p. 310. ^ Allgemeine Anatomic. 
