108 ANTHROPOLOGY. 
essential point from that of the spine: namely, in that it forms a periosteum 
to the inner surface of cranial bones. It adheres closely to the whole 
interior of the cranium, and the free communication between the vessels 
of the dura mater and those of the bones serves materially to enhance the 
connexion between this membran® and the osseous surface. On the roofs 
of the orbits, the wings of the sphenoid bones, the petrous portions of the 
temporal ea the margin of the petipital foramen, and See the 
sutures, the ee is very intimate. 
The cranial dura mater is not a simple bag. From its internal surface 
partition-like processes pass inwards, which serve to separate certain subdi- 
visions of the encephalon or brain. These are the falx cerebri, the tentorium 
 eerebelli, and the falx cerebelli. 
The jes cerebrt 1s a process of fibrous membrane corresponding to the 
mesial plane, and lying in the great median fissure of the brain, where it 
separates the lateral hemispheres from each other. Its shape is falciform; 
its superior convex border corresponds to the frontal and sagittal sutures, 
and incloses the great longitudinal sinus; its inferior border is concave and 
much shorter than the superior, and corresponds to the superior surface of 
the corpus callosum, which connects the hemispheres of the brain. In front 
the falx is narrow, and almost pointed; it embraces the crista galli of the 
ethmoid bone, which appears to be inclosed between its layers. The falx 
cerebri contains within it, along its posterior border, a large vein, known 
as the inferior longitudinal sinus. 
The tentorvum cerebelli is continuous on each side with the posterior 
border of the falx cerebri. This process is nearly horizontal in direction. 
It forms a vaulted roof to a cavity, whose floor corresponds to the occipital 
fossee, and in which the cerebellum is lodged. The posterior and outer edge 
adheres to the occipital bone, and to the posterior border of the petrous 
portion of the temporal. The occipital portion of this edge contains a con- 
siderable part of the lateral sinus, the portion adhering to the petrous bone 
containing the petrosal sinus. The anterior or inner margin of the tento- 
rium is concave, and free in the greater part of its extent. It is attached 
by its anterior extremities to the anterior clinoid processes, to reach which 
it crosses the posterior border. 
_ From the inferior surface of the tentorium cerebelli at its posterior edge, 
a short and thick fold of very slight depth descends to the posterior edge of 
the foramen magnum. This is the falx cerebellu. It corresponds to the me- 
dian notch between the hemispheres of the cerebellum. Its anterior border 
is slightly concave. ‘T'wo veins, called occipital sinuses, are contained in it. 
Although the internal surface of the cranial dura mater usually presents 
the same smooth appearance as has been referred to in that of the spine, yet 
an exception is found along the great longitudinal sinus, in the occasional 
presence of small glandular bodies growing from the arachnoid membrane, 
and causing a peculiar cribriform appearance in the dura mater. These 
bodies, called glandule or glands of Pacchioni, are in all probability not 
oma structures, but are rather morbid products of the arachnoid produced 
by ie ag cerebral excitement. 
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