688 BLOOD-VASCULAR SYSTEM OF THE HORSE 
The ventral longitudinal or sagittal sinus (S. sagittalis ventralis) is much 
smaller than the dorsal sinus.t. It runs backward on the corpus callosum in the 
concave edge of the falx cerebri, and joins the great cerebral vein to form the straight 
sinus. It receives veins from the medial surface of the cerebral hemispheres and 
from the corpus callosum. 
The straight sinus (S. rectus) proceeds from the junction of the ventral longi- 
tudinal sinus with the great cerebral vein behind the corpus callosum. It ascends 
in the falx cerebri, inclining backward, and joins the dorsal longitudinal sinus at 
the confluens sinuum. 
The transverse sinuses (Ss. transversi), right and left, proceed laterally from 
the confluens smuum; they pass outward in the transverse grooves of the parietal 
bones, enter the temporal canals, and are continued by the dorsal cerebral veins 
to the superficial temporal veins. They receive the dorsal petrosal sinuses, veins 
from the posterior part of the cerebrum and from the corpora quadriceminal and 
the posterior meningeal vein. The two sinuses are connected by the sinus com- 
municans, which extends across the cranial vault in a channel in the base of the 
internal occipital protuberance. 
The dorsal petrosal sinuses (Ss. petrosi dorsales) ascend in the tentorium 
cerebelli and join the transverse sinuses near the internal opening of the temporal 
eanal. Each is the direct continuation of the vena rhinalis posterior and receives 
the vena basilaris cerebri. There is sometimes an accessory petrosal sinus along- 
side of the chief sinus, which is formed by the confluence of veins from the pons 
and medulla oblongata. 
The occipital sinuses (Ss. occipitales) are situated in the dura mater on each 
side of the vermis cerebelli. They communicate in front with the sinus communi- 
cans, and one of them is continued posteriorly by the dorsal spinal vein. Each 
sinus is connected by a communicating branch with the transverse sinus and with 
the ventral petrosal sinus. The right and left sinuses are connected by anasto- 
motie branches, so that the arrangement is more or less plexiform. They re- 
ceive veins from the cerebellum, medulla oblongata, and diploé. 
The basilar system consists of the following: 
The cavernous sinuses (Ss. cavernosi) lie in the medial grooves of the root of the 
temporal wings of the sphenoid bone at either side of the pituitary fossa. The two 
are connected by a wide transverse branch, the intercavernous sinus (Sinus inter- 
cavernosus), behind and below the posterior part of the pituitary body.? Each is 
continuous in front with the ophthalmic vein and below with the ventral petrosal 
sinuses; it communicates also by small anastomotic veins with the basilar plexus. 
The third, sixth, and the ophthalmic and maxillary divisions of the fifth nerve lie 
along the lateral wall of the sinus. The internal carotid artery traverses the sinus 
and is connected with its fellow by a transverse branch which lies in the inter- 
‘avernous sinus. An oval opening in the floor communicates with the ventral 
petrosal sinus and transmits the internal carotid artery. 
The sinus is not subdivided by strands of fibrous tissue as in man, but a few delicate bands 
attach the artery to its wall. 
The ventral petrosal sinuses (Ss. petrosi ventrales)* lie along the borders of 
the basilar part of the occipital bone, enclosed in the thick dura which closes the 
foramen lacerum. The anterior part extends about half an inch (ca. 12 mm.) 
under the temporal wing of the sphenoid. Here communications exist with veins 
in the pterygopalatine fossa. The posterior end is bulbous and lies in the condy- 
i ‘it is also termed the vena corporis callosi major. 
? A small anterior intercavernous sinus may connect the two cavernous sinuses in front of the 
pituitary gland. Mobiliostates that he has seen the cavernous sinus having a blind anterior end, 
the ophthalmic vein passing laterally to the ventral petrosal sinus. 
’ These are termed the subsphenoidal confluents by Chauveau and M’Fadyean. 
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