_ from parts exterior to the cranium. 
NERVOUS CENTRES.: (Homan Anatomy. Tar MentnGes.) 
The sinuses of the duru mater.—At certain 
situations, processes of the inner membrane of 
the venous system are included in canals formed 
by the separation of the lamine of the dura 
mater. ‘The channels that are thus formed for 
the passage of the venous blood do not admit 
of being dilated beyond a certain size, and in 
this consists an important peculiarity in the 
venous system within the cranium. These 
channels empty themselves into the internal ju- 
gular vein, which thus forms almost the sole 
channel by which the venous blood is returned 
from the brain and its membranes as well as in 
a great measure from the bones of the skull. 
And thus is explained the rapid influence which 
_ is produced upon the brain by any impediment 
_ to the passage of the blood through the superior 
_ vena cava. 
It is important to notice that the sinuses 
- communicate with and receive blood from cer- 
tain external veins which carry blood derived 
Among 
these may be enumerated the ophthalmic vein, 
and several small veins in the neighbourhood of 
the mastoid and condyloid processes, and in 
the parietal bones. 
e following sinuses may be described. 
| The superior longitudinal sinus. — This 
sinus corresponds to the superior margin of the 
_ falx cerebri. It commences very narrow by one 
_ Or two small veins from the dura mater in the 
vicinity of the crista galli and cribriform plate 
_ of the ethmoid bone. Thence it proceeds back- 
wards, gradually increasing in calibre, and it 
terminates a little above the internal occipital 
‘protuberance by communicating with a small 
cavity or reservoir, situated between the layers 
of the dura mater there, which is called Tor- 
cular Herophili. 1f a vertical section of this 
sinus be made in the transverse direction, it will 
be seen to be triangular in shape, the apex cor- 
Tesponding to the falx, the base slightly curvi- 
linear and lodged in the groove which passes 
along the median line of the cranial vault. 
When the sinus is laid open in its length by 
slitting up its superior wall, we find that its 
Sides are perforated by a great number of mi- 
nute orifices, which are the openings of veins 
passing into it from the dura mater and from 
brain itself. These veins pass into the 
sinus chiefly at right angles to it, or in the 
direction from behind forwards; a few, situate 
in front, enter the sinus from before backwards. 
In the interior of the sinus we observe little 
bands (trabecule of Haller, chorde Willisii ), 
stretching across from right to left, connected 
only with the lateral walls and leaving a free 
Space above and below them. These bands 
are numerous, and various as regards breadth. 
Haller has.seen them so numerous that they 
appeared like a septum dividing the sinus into 
two portions, of which the superior was the 
er. 
walls of the sinus, towards its inferior 
angle, have frequently a cribriform appearance, 
which puts on somewhat the aspect of erectile 
tissue. There is no appearance of valves in 
the interior of the sinus; frequently, however, 
the oblique entrance of a small vein into the 
631 
sinus produces a fold near the venous ag-rture, 
which, under the retrograde pressure of the co- 
lumn of blood, might close the orifice, and 
probably, when the veins open into the sinus 
from behind forwards, they may be protected 
fiom the regurgitation of the blood by this 
mechanism. 
Several of the small bodies, previously al- 
luded to bythe name of Pacchionian glands, 
project into the cavity of the sinus through 
apertures in its wall. They appear as if they 
had worn their way by pressure and friction 
through the walls of the sinus, and it is here 
that the cg of an erectile structure is 
most manifest. We cannot suppose that these 
bodies are bathed in the blood of the sinus, but 
rather that they push the lining membrane of 
the sinus before them. It has been supposed 
that these bodies are natural structures destined 
to perform a mechanical office somewhat on 
the principle of the ball-valve, but they are 
frequently absent altogether, and when present 
they have no constant relation to the venous 
orifices. 
The inferior longitudinal sinus (sinus infe- 
rior falcis ) is a small vein lodged in the inferior 
part of the falx cerebri, running parallel to and 
a little above its inferior margin for about the 
two posterior thirds of its length. It gradually 
increases in calibre from before backwards, 
being formed by tributary veins from the falx ; 
it bie into the strait sinus. 
he strait sinus corresponds to the middle 
line, at the place where the falx cerebri unites 
with the tentorium cerebelli. It seems to be 
enclosed between the layers of the former. Like 
the cther large sinuses, it presents in its section 
the form of a triangle, whose base is inferior. 
Its direction is from before backwards and a 
little downwards, with a slight degree of curva- 
ture corresponding to that of the tentorium. It 
corresponds at its commencement to the space 
between the posterior reflected portion of the 
corpus callosum and the quadrigeminal bodies, 
and here it receives two large veins (vene magne 
Galeni), which carry the blood from the inte- 
rior of the ventricles, and a third vein, the in- 
ferior longitudinal sinus. It opens into the 
conflux of the sinuses or torcular by a round 
Opening or sometimes by two openings, sepa- 
rated by a slip of fibrous membrane. This 
sinus likewise receives veins from the inferior 
surface of the posterior and middle lobes of 
the brain, and from the superior surface of the 
cerebellum. 
At the posterior extremity of the straight sinus 
we find a reservoir somewhat polygonal in 
shape, which corresponds to the occipital pro- 
tuberance; this is called the Torcular Hero- 
phili,* (the press of Herophilus,) the conflux 
of the principal sinuses of the dura mater; it 
has six openings, one for the superior longitu- 
* This absurd name might with great advantage 
be discarded, for it seems quite uncertain what 
precise part Herophilus intended to apply it to. 
The term proposed by Cruveilhier is much better, 
the occipital conflux of the sinuses. Various other 
names were applied to it formerly, such as Lacuna, 
platea, pelvis, laguncula, 
