This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book
(without typos) from the publisher. Not indexed. Not illustrated.
1917 Excerpt: ...envelope of the leptomeninges and the central
nervous system. But there is a tendency to regard the arachnoid and
pia mater as constituting one structure--the leptomeninges or
"pia-arachnoid," in the terminology of Middlemass and Robertson39).
This difference of opinion in regard to the two inner meninges is
due to their structural and intimate relationships. The arachnoid
may well be assumed to be a single membrane, worthy of being
regarded as a single structure if one considers only its outer
continuous membrane as the essential structure. But the inner
surface of this membrane sends processes inward to fuse with the
pia mater, which is so closely applied to the nervous tissue. These
processes divide the subarachnoid space (included between arachnoid
and pia) into the well-known meshes in which the cerebro-spinal
fluid circulates. From the standpoint of these channels (the
subarachnoid spaces) the arachnoid constitutes the parietal and the
pia the visceral layer. Thus the intimate structural unity of the
two membranes seems, in the opinion of many investigators, to
warrant their designation as a single membrane. This view, however,
has been strongly opposed by Poirier and Charpy45), who considered
the distinction of three meninges very essential. Hence, in
considering the transformation of tissues in the embryo, regard
must be had for the dura as a well-differentiated structure, and
for the leptomeninges as units, but certainly to be regarded from
the standpoint of the subarachnoid spaces. In this connection
Sterzi's(53) observations on the comparative anatomy of the
meninges are of interest. It will be recalled that the dura in
lower forms becomes well established before the leptomeninges
emerge from a primitive mesenchyme. THE PERIAXIAL MESENC...
|Country of origin:
Carnegie Institution of Washington
||246 x 189 x 3mm (L x W x T)
||Paperback - Trade
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