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57G DENTAL EMBRYOLOGY AND HISTOLOGY. ;

Now, if we had taken a portion of the same bone, when fresh, and
placed it in dikite picric acid and decalcified it, afterward cutting thin
sections and staining them with picrocarmine, we should not have seen
the cavities which we observed in the section of dried bone ; for while
by the process of drying we destroyed the contents of the cavities, by
the use of the picric acid we preserved their contents.
In lacunae we find bone-cells ; in canaliculi, processes of bone-cells
in Haversian canals, capillary vessels.
By studying sections prepared according to the methods above de-
scribed, we are able to understand the real formation of bone. It is
needless to remark that our present knowledge of bone-formation is the
result of the accumulated research and careful observation of scientists
for many generations.
The general misuse of the terms lacunce, canaliculi, and Haversian
canals attests the need of a more thorough understanding of the pro-
cess of bone-formation. A brief recapitulation of the more important
points may make the subject clearer to the reader.
The osteoblasts do not become calcified, but remain as the life-occu-
pants of the calcospherules, and by reason of such occupancy make it
possible for us to produce, by drying, the cavities known as lacunse.
Calcification is a process of secretion around, and not in, the cell. The
mollusk secretes upon, and not in, its body, and the secreted portion of
its shell does not contain organic tissue. The only living matter
found therein is the body of the mollusk, which we can extract and yet
Fig. 316.

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Transverse Section of Compact Tissue (of Humerus). (Magnified about l.iO diameters ) Three of
the Haversian canals are seen, with their concentric rings; also the lacunte, with the canaliculi
pxtendinp; from them across the direction of the laniellre. The Haversian apertures had become
filled with air and dfbris in Rrindinj,' down tlic section, and therefore appear bhick in the figure,
wliich represents the object as viewed with transmitted light.
leave the shell as perfect a shell as before the death of its occupant.
We do not think of attributing to the ."^hell the possibility even of such
a thing as an inflammatory process, for the reason that the shell is