630 
In front of the dura mater and situate between 
the outer edge of the posterior common liga- 
ment of the vertebre and the pedicles, we find 
two remarkable venous sinuses which extend the 
whole length of the vertebral column, from the 
occipital foramen to the sacral region (fig. 360). 
_ Fig. 360. 
~ 
Spinal sinuses viewed from before. 
(After Breschet.) 
The anterior part of the basis cranii and the face 
have been removed, as also the bodies of the 
vertebra. 
i, lateral sinus descending to form its junction 
with the jagular vein; c, cavernous sinus; 0, ver- 
tebral artery, the longitudinal sinuses with their 
transverse connecting veins, lying immediately be- 
hind the bodies of the vertebre. The interior 
petrosal and the cavernous sinuses appear like con- 
tinuations of them within the cranium, and the 
transverse and circular sinuses are analogous to the 
transverse spinal branches. 
These veins are loosely covered by a thin pro- 
cess, which is prolonged from each margin of 
the posterior common ligament, and which is 
sufficiently transparent to allow them to be seen 
through it without removing it. They have 
been known since the time of Fallopius, and 
were described by Willis as the longitudinal 
spinal sinuses. In calibre they present many 
inequalities, being dilated at one part and con- 
stricted at another, according to the number 
and size of the vessels which communicate 
with them. The sinuses of opposite sides run 
rallel to each other and communicate by cross 
ranches, which pass between the posterior sur- 
face of the body of each vertebra and the pos- 
NERVOUS SYSTEM. (Nervous Centres. Tut Mentners.) 
terior common ligament. These cross branches 
present the same characters as the sinuses them- 
selves, being of variable calibre, and presenting 
the greatest degree of dilatation at their middle. 
At this point these branches receive veins which | 
emerge from the spongy texture of the bodies of 
the vertebre (basi-vertebral veins of Breschet) 
(fig. 361,d). The vertebral sinuses diminishin 
fe - 
Fig. 361. a4 
Ages 
; Ay 
Basi-vertebral veins, convergi the spongy stru 
ture of the sedge?’ he coveain e 
size at the highest part of the vertebral canal, a 
passing through the anterior condyloid foramina 
communicate with the internal jugular vei 
In the sacral region they diminish considerab 
likewise, and are lost in becoming conti 
with the lateral sacral veins and other 
veins in that region; and they communic 
with the deep and superficial vertebral veins 
the neck, with the intercostal veins in the bar 
and with the lumbar ones in the loins. Th 
evidently differ from the sinuses of the crat 
dura mater in not being enclosed betweet 
layers of fibrous membrane as those ve 
Bloodvessels of the cranial dura mat 
The bloodvessels of the cranial dura 
are much more numerous than those 
spinal, in consequence, no doubt, of that mi 
brane performing the office of a periosteu 
the cranial bones. The arteries are de 
from numerous sources; in front from 
ophthalmic and ethmoidal arteries, — 
middle from the internal maxi 
the middle meningeal, which enters d 
at the foramen spinosum, and by small t 
from the internal carotid which 
called inferior meningeal arteries. Post 
the vertebral, the occipital, and the asce 
pharyngeal supply branches which go’ 
name of posterior meningeal arteries. 
y The veins of the dura mater are form 
rly to those in other parts, being deri 
radicles which take their rise in the mem 
itself as well as from the osseous walls ¢ 
cranium, from the diploic veins of those! 
(See Bont, figs. 187, 188, vol.i.) All oft 
with the occasional exception of one or 
which accompany the middle meningeal ¢ 
and pass out at the foramen spinosum, 
their blood into the great venous canals 
closed between the lainine of the duran 
which are called Sinuses. 7" 
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