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Proceedings of Royal Society of Edinburgh. [sess. 
lage. There is an absence of vessels at the ossifying junction. The 
typical organ-pipe arrangement of structures at the ossifying junction 
is either not recognisable at all, or only here and there, and that 
faintly. In several of the bones we further noticed that the zone 
of cartilage immediately adjoining the ossifying junction was sharply 
defined or cut off from the main mass of cartilage above it by a 
curved line or layer, in which the cartilage matrix is partially 
fibrillated, and the cells flattened and crowded together, resembling 
the tissue arrangement seen in perichondrium. 
The appearances described sufficiently account for the remarkable 
external appearances of the long bones. 
Previous observers wffio have examined specimens similar to that 
under consideration, describe as characteristic, the occurrence of an 
intrusion from the periosteum between the diaphysis and epiphysis, 
which interferes with the development of bone from the latter 
(Eberth, Urtel, Bode). We believe this appearance to be fallacious ; 
it is merely the result of the disproportion in size between the shaft 
and the terminal cartilage, together with the abrupt curvature of the 
shaft close to their junction. The apparent intrusion is only seen 
at the concavity of the curve, in sections close to the surface of the 
bone. In making our serial sections of the entire bone in its long 
axis from the surface inwards, we observed that no such intrusion 
was visible when the level was reached at which complete sections 
were obtained. 
The other bones were examined on similar lines ; the seventh rib, 
for example, with its cartilage, presented appearances which might 
be exactly compared to those seen in one-half of a long bone ; the 
short diaphysis of the rib consisted entirely of periosteal bone, cup- 
shaped at the costal end so as to embrace the cartilage, — a similar 
arrest of endochondral ossification being observed at the ossifying 
junction. 
In the bodies of the vertebrae, the os calcis and astragalus, there 
was a complete arrest of the ossifying process at the junction of the 
small central nucleus with the surrounding cartilage; the bone 
already formed being for the most part nietaplastic, while the 
marrow was deficient in large vessels and in giant cells. It is 
obvious that the arrest of ossification in these bones is not to be 
ascribed to a continuous and excessive formation of periosteal bone 
