632 
dinal sinus above; one for the straight sinus in 
front; two for the lateral sinuses on each side ; 
and two for the occipital sinuses inferiorly 
(fig. 362, t). 
Posterior part of the cranium removed, to shew the 
dura mater and the superior itudinal, and the 
lateral sinuses, with the torcular Herophili. 
é, lateral sinus ; ¢, torcular Herophili; s, superior 
longitudinal sinus. 
Lateral sinuses —From each side of the con- 
flux of the sinuses, there proceeds in a some- 
what serpentine course outwards, downwards, 
and forwards, a wide canal, the largest of the 
sinuses, which conveys the blood from the 
torcular to the internal jugular vein. A groove 
exists on each side of the internal occipital pro- 
tuberance, for the reception of this sinus, which 
marks the occipital bone, the mastoid portion 
of the temporal, and a small portion of the 
occipital bone again. In a great portion of 
their course, the lateral sinuses correspond to 
the posterior margin of the tentorium cerebelli, 
as far forwards as the mastoid portion of the tem- 
poral bone. Here each sinus winds downwards 
to reach the jugular foramen in the posterior 
lacerated opening. These sinuses are never 
equal; that of the right side being, with few 
exceptions, the larger, a circumstance which 
Vicq d’Azyr, Soemmering, and Rudolphi attri- 
buted to the fact that most persons sleep on the 
right side, on which account the blood is apt 
to accumulate to that side. They are more 
capacious at their termination in the jugular 
veins than at their commencement from the 
torcular. The inner surface of this sinus is like 
that of all the others; it is not, however, tra- 
versed by any of the bands which are found so 
numerous in the longitudinal sinus. Cruveil- 
hier states that he once saw in the horizontal 
rtion of this sinus, a few of the Pacchionian 
ies. 
In its course each lateral sinus receives veins 
NERVOUS SYSTEM. (Nervous Centres. Tut Meninces.) 
4 
from the inferior surface of the brain and supe- — 4 
rior of the cerebellum; it also receives the supe- 
rior petrosal sinus near the base of the us 
portion of the temporal bone. A large id 
vein communicates with this sinus and pene- — 
trates to the exterior, where it forms one of the 
principal sources of the occipital vein, thus 
establishing a free and direct communication — 
between the circulation within and that with- 
out the cranium.* Near the josular a 
the lateral sinus receives the inferior petrosal. 
None of the sinuses has been more fre- 
quently the seat of inflammatory disease tha 
the lateral. Being the principal channel for 
the return of the venous blood from the in- ~ 
terior of the skull, a slight morbid action within 
them can scarcely fail to induce a material de- 
rangement of the cerebral circulation, and the 
nearness of their position to the cerebellum and — 
to the posterior lobes of the brain renders it 
very unlikely that those parts would escape 
participating in any acute disease which might 
arise within it. - 
Occipital sinuses. — These are small 
lodged between the layers of the falx cerebe 
They collect the blood from the dura mater and 
from the cranial bones in the immediate vici- 
nity of the posterior margin of the fe 
magnum, and from thence they pass upward 
and inwards to open into the lower part of th 
torcular. Cruveilhier suggests that the direc. 
tion and position of the occipital sinuses ar 
best indicated by describing them as being th 
cords of the arcs which the lateral sinuse 
form. 
Petrosal sinuses. — These sinuses are s¢ 
named from their connection with the pet 
portion of the temporal bone. The 
petrosal sinus corresponds, on each side, to th 
posterior superior edge of the Dor 
along the three outer fourths of which a groow 
exists for its reception. This groove is inter 
rupted in front by a depression in which th 
tifth nerve is lodged, so that at this place th 
nerve lies between the sinus and the bone. T 
superior petrosal sinus is about large eno 
contain an ordinary sized surgeon’s pre 
communicates with the lateral sinus post 
and with the cavernous sinus in front, an¢ 
its course it receives several small veins ff 
the dura mater in the middle fossa of the 
nium. It receives a vein from the anterior p 
tion of the corresponding hemisphere of 
cerebellum, and also, sometimes, one from 
inferior surface of the brain. Small veins 
the pons Varolii empty themselves into its 
terior extremity. re! 
The inferior petrosal sinuses also forr 
additional channel of communication bety 
the lateral and cavernous sinuses. h 
larger but shorter than the superior. Inst 
ation they correspond to the interval betwee 
the petrous bone and the occipital. They ops 
into the inferior portion of the lateral sint 
before it unites with the jugular vein. i 
Transverse sinus.—This sinus establis 
a communication between the 
Se 
per 
* Cruveilhier, An, Desc. t. iii. p. 268. 4 
