able interspace between the dorsal extremities of the laminæ. The transverse
process is situated between the upper extremities of the articular surfaces, external
to the base of the ossified neural arch. In a disarticulated skeleton, the vertebral
column of which is 19’50 inches in length, the atlas was found to be completely
ossified, but its constituent elements, the neural arch and hypapophysis, were not
united. The articulating surfaces are divided in their lower thirds by the suture
corresponding to the neurocentral suture of the other vertebræ, and which, when
the vertebra is in position with the axis, is seen to be continuous with the outer
margin of the odontoid. The laminæ have almost united with each other. The
transverse process, which is ossified, is thus placed high above the neurocentral
suture, and corresponds to the superior processes of the cervical vertebræ as supposed
by Eschricht. I t is continuous with the neural ossification, of which it is an
exogenous product. The lower arch is also fully ossified, and by the anterior
surface of its upper extremity it contributes to form the lower third of the anterior
articular surfaces of the atlas.
In the axis of the foetus, the pedicles, posterior zygapophyses, and laminæ are
ossified, but an interspace between the laminæ above, and a considerable area external
to the centrum and involving the transverse process, are cartilaginous. The transverse
process is borne on the outside of the middle of the anterior articular surface
immediately below the inferior ossified extremity of the pedicle. In another specimen,
the process is seen to be entirely above the neurocentral suture and is imperforate,
so that Eschricht’s view of the double nature of this process is not supported
by these facts. In the other foetus, there is no line of separation between the
centrum and the odontoid, but, in the anterior extremity of the latter, there is a well-
developed ossified mass. Anteriorly, the ossification of the neural arch is seen to be
s p r e a d i n g downwards into the anterior zygapophysis. The older specimen displays a
most instructive condition of the parts. The neural [arch, articular facets, and transverse
process are fully ossified, with the exception of the tip of the latter. The neurocentral
suture is intact, cutting through the lower third of the anterior articular facets»
with the transverse process wholly above it and defining the outer limit of the odontoid.
This is fully ossified, but separated by a line of suture from the body of the axis ;
yet showing its double nature by a constriction in the middle of the posterior margin
of its lower surface, the halves of the centrum being still distinct and bulging
below to constitute the hypapophyses.
In the third cervical, the inferior extremity of the ossified neural arch is separated
by a cartilaginous interval from the body of the vertebra ; this interval being continuous
externally with a cartilaginous process investing the side of the centrum.
In the more matured specimen, a small foramen perforates the inferior extremity
of the base of the right transverse process; but the neurocentral suture being intact,
the whole of the process is seen to lie above it.
In the fourth cervical vertebra of the foetus, the lateral cartilaginous mass external
to the centrum is divided into two portions. The superior, lying below the neural
ossification, is broad and notched at its extremity, and is separated below by another
notch from an inferior process, which, however, is continuous at its base with the
foramen. In an older animal, the vertebra is ossified, but the neurocentral suture
cuts through the notch which separates the superior from the inferior process, and
the latter is seen to be an autogenous element developed at the inferior external angle
of the centrum below the neurocentral suture, while the superior transverse
process, as in the preceding vertebrae, is an exogenous product of the neural
arch.
In the fifth and sixth vertebrae, a similar condition of things exists, only the
inferior autogenous process becomes more strongly developed as it is traced to the
sixth, where it occupies the same position as in the fourth vertebra.
In the seventh vertebrae of the foetus, there is a cartilaginous interval between the
neural laminae; the transverse process is unossified, the pedicles are separated by a
cartilaginous interspace from the centrum, and the position of the inferior transverse
process on the side of the centrum in the previous vertebrae is occupied by the
facet for the head of the rib. In the more mature skeleton before me, the neural
laminae have nearly united; the superior transverse process is fully ossified; and the
neurocentral suture is at a higher level than in the preceding vertebrae and has a
more outward course. A portion of the head of the first rib has been brought away
in separating the vertebra from the first dorsal, and is attached to the outer
extremity of the neurocentral suture, between the external margin of the base of
the pedicle and the lateral surface of the centrum, being chiefly applied to
the latter and simulating the inferior transverse process of the sixth cervical
vertebra.
There is this remarkable fact also connected with this same animal that the
superior transverse process of each side bears at its extremity what must be
regarded as the rudiment of the tubercular portion of a cervical rib, much more
intensely developed on the right than on the left side. This condition of things is
the very opposite of that which prevails in the last dorsal vertebra, in which the rib
is borne on the extremity of the autogenous transverse process of the centrum of
the tenth dorsal; which process is serially homologous with the autogenous transverse
process of the lumbar region and with the similarly originated processes of the
cervical vertebrae. I t may be regarded as an enormously developed epiphysis of
the superior transverse process simulating the portion of the rib distal to the
tubercle; but .it must be kept in mind that no other of the epiphyses of the
vertebral process are developed.
The neurocentral suture in all the cervical vertebrae is intact, but in a still
older skeleton the suture only exists in the seventh vertebra, having disappeared in
all the others, and the inferior transverse processes are completely united with their
respective centra.
In the dorsal region, the tubercles become more and more approximated to the
heads of the ribs as they are traced backwards, till at last in the sixth, but more perfectly
in the eighth, rib they are merged in one articular surface, which is exclusively
applied to the transverse process of that vertebra which occurs on the side of the
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