120 
MESSRS. J. TOMES AND C. DE MORGAN ON THE 
those of the pelvis, be indented by firm pressure with the finger. Such bones, after 
maceration, contain within the spaces enclosed by the cancelli, a white powder, which 
readily falls out if the bone be broken. If a little of this powder be mounted in 
Canada balsam, and placed in the field of the microscope, the observer will see that 
it is mainly composed of large nucleated cells, some of which are detached, others 
united into masses. 
The isolated cells have a spherical or oval form, and appear to consist of a granular 
nucleus surrounded by a very thick cell-wall, external to which we commonly find an 
aggregation of granular matter, indefinite in amount and presenting a ragged outline 
(Plate VII. fig. 15). The cells which are united into masses are connected by this 
granular matter, or ossified blastema, as it might perhaps be called. The cells them- 
selves are similar to the loose ones, excepting that in some cases their character is 
rendered more apparent by the nucleus assuming the form of a lacuna. If a section 
of the bone be examined, similar cells will be found adherent to the walls of the 
Haversian canals, with the canaliculi of contiguous lacunm advancing into them, 
while the nuclei of the adherent cells are assuming the form of lacunae and throwing 
out canaliculi. 
Again, in the substance of the bone, the outline of the formative cells, similar in 
size and shape to the loose ones, may be in places recognized, having lacunae and 
canaliculi as their centres. The recognition of these ossified cells in their isolated 
state will be followed by the observation of similar cells occupying the Haversian 
canals and cancellar spaces in the majority of microscopic preparations of adult bone 
(Plate VI. fig. 5 a) ; and the same may sometimes be seen on the outer surface of bone 
(Plate VII. fig. 18). The appearance of the cells is, however, liable to be modified by 
the various circumstances which operate upon growing bone, such as the presence 
of a tendon, or of a large pulsating vessel, or in fact, by pressure from any cause. 
Thus if situated in the immediate neighbourhood of a tendon, they assume an elon- 
gated form ; while on the other hand they may be flattened by pressure. 
It has been thought desirable to describe the ossified lacunal cells at this place, on 
account of their frequent occurrence in adult bone (Plate VI. fig. 5 a, and Plate VII. 
figs. 16 and 18). 
Bone Tissue. — Hitherto we have confined our description to the forms in which 
the bone substance is arranged, as into laminoe, Haversian systems, &c. We have 
now to consider the ultimate structure of the tissue itself. But little has been said 
upon this point until within the last ten years. In the ‘Physiological iinatomy’ of 
Dr. Todd and Mr. Bowman*, it is stated that bone is made up of an aggregation of 
granules in a scarcely distinguishable matrix. Latterly, other views have been pro- 
posed. Dr. Sharpey has advanced the hypothesis, that although the bone developed 
in cartilage is at one period granular'|~, a reticulate fibrous arrangement of the elements 
* Dr. Todd and Mr. Bowman, Physiological Anatomy, page 108. 
t Dr. Quain’s Anatomy, edited by Mr. Quain and Dr. Sharpey, page 157. “ The primary osseous 
matter forming the original thin walls of the areolm is, as Mr. Tomes observes, decidedly granular, and has a 
