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MESSRS. J. TOMES AND C. DE MORGAN ON THE 
a transverse section of the latter the parietes are readily recognized, as shown in 
figure 11, Plate VII. 
In a longitudinal section of Haversian systems we have the laminae on either side 
of the canals cut at right angles, or nearly so, while immediately over the canals they 
are exposed in their breadth ; in the one instance we look upon the cut edges, in the 
other upon the surface of the laminae. The lacunae in the two parts present dif- 
ferences in outline. In the former part they resemble those seen in the Haversian 
systems divided transversely, in the latter they approach a circular, or slightly oval 
figure, and send out canaliculi indifferently from all parts of their circumference. 
After examining the lacunae from these three different points of view, it will be mani- 
fest to the observer that the normal form is that of a greatly compressed hollow 
sphere or oval, from which numerous minute tubes are continued. To this prevailing 
form we find numerous exceptions, which, although of not unfrequent occurrence, 
form but a small part of the whole number that may be seen in an ordinary prepara- 
tion. The outlines assumed by the exceptional lacunae are too varied and too irre- 
gular to admit of such a description as would embrace every departure from the 
ordinary form. It is however worthy of mention, that lacunae may sometimes be 
met with, normal in form, but of three times the usual dimensions. 
What has been said of the lacunae of the Haversian systems will of course apply 
also to those occupying parts of systems known under the name of interstitial laminae. 
In the circumferential laminae the lacunae are for the most part similar to those 
already described. But we have in this situation what may perhaps be regarded as 
modified lacunae, presenting themselves in the form of elongated tubes arranged in bun- 
dles, or occurring singly, and passing more or less obliquely from the surface towards 
the interior of the bone (Plate VII. fig. 13). When these tubes attain a considerable 
length they are commonly bent at a sharp angle once or twice in their course, and 
at each flexure change their direction, presenting sometimes a loose resemblance to 
the letter When these tubules are divided transversely they exhibit parietes. On 
tracing them in parts abounding with lacunae, it will be seen that they form lateral 
connections with the canaliculi, at the same time that they cross these as well as the 
lacunae and laminae obliquely. The presence of the oblique tubes is not however con- 
stant. In one part of the circumferential laminae they will be abundant, while in 
another they will be sparingly present or altogether absent. Then, again, they may 
be seen in one series of laminae, while in the contiguous set they are absent, but may 
reappear in a third and more deeply-seated series. They are, however, we believe, 
strictly confined to the limits of the circumferential laminae, and are seldom present 
unless these are tolerably abundant. 
The lacunae situated in the transparent non-laminated bone, which is sometimes 
found on or near the surface, and to which we have before alluded, are less com- 
pressed in form than those hitherto described. They are subject to great irregularities 
of outline, and send off" canaliculi equally from all parts of their circumference, thereby 
