650 



THE BLOOD-VASCULAR SYSTEM 



the right, and ends in the right transverse Clateral) sinus; the straight sinus then 

 usually terminates in the left transverse (lateral) sinus. 



Occasionally, however, the superior sagittal sinus ends in the left transverse sinus, the 

 straight then passing into the right. At the angle of union between the superior sagittal 

 sinus and the transverse sinus into which it empties there is a dilation, the confluens sinuum 

 or torcular HerophiU. At this point there is a communication between the right and left trans- 

 verse sinuses. In some cases the communication is so free that the blood from the sagittal 

 sinus flows almost equally into each transverse sinus. The confluens may communicate with 

 the occipital vein through the occipital emissary vein [emissarium occipitale], which, when present 

 passes through a minute foramen in the occipital protuberance. 



(2) The inferior sagittal (or longitudinal) sinus [sinus sagittalis inferior] (fig. 

 515) is situated at the free margin of the falx cerebri. Beginning about the 

 junction of the anterior with the middle third of the falx, it is continued backward 

 along the concave or lower margin of that process to the junction of the falx with 

 the tentorium, where it ends in the straight sinus. The sinus is cylindrical in 



Fig. 514. — The Venous Sinuses. 

 (From a dissection by W. J. Walsham in St. Bartholomew's Hospital Museum.) 



Meningeal branch of an- 

 terior ethmoidal artery 



Meningeal branch of pos 

 terior ethmoidal artery 



Middle meningeal 

 artery 

 Ophthalmic division of 

 trigeminus 



Oculomotor nerve 

 Cavernous sinus 

 Trochlear nerve 

 Auditory & facial nervei 

 Superior petrosal sinus 

 Inferior petrosal sinus 

 Petro-squamous sinus 



Spinal accessory nerve 

 Sigmoid portion of 



transverse sinus 

 Posterior meningeal 

 branch of vertebral 

 artery 



Left marginal sinus 



Left transverse sinus 

 Superior sagittal sinus 



Circular sinus 

 Carotid artery 



-Abducens nerve 

 Basilar artery 

 Basilar plexus of 



veins 

 Auditory artery 

 Vertebral artery 

 Glosso - pharyngeal 

 and vagus nerves 

 Anterior spinal 

 "7 artery 



/ Hypoglossal nerve 

 Spinal accessory 

 nerve 



Right marginal sinus 



Occipital sinus 



Right transverse sinus 



shape and of small size, and receives some of the inferior frontal veins of the brain, 

 some of the veins from the medial surface of the brain, and some of the veins of the 

 falx. 



(3) The straight sinus [sinus rectus] lies along the junction of the falx cerebri 

 with the tentorium cerebelli. It is formed by the union of the great cerebral vein 

 (of Galen) and the inferior sagittal sinus. It receives in its course branches from 

 the tentorium cerebelli and from the upper surface of the cerebellum. It runs 

 downward and backward to the internal occipital protuberance, where it ends in 

 the transverse sinus opposite to that joined by the superior sagittal sinus. On 

 section it is triangular in shape, with its apex upward. 



(4) The occipital sinus [sinus occipitalis] (fig. 514) ascends at the attached 

 margin of the falx cerebelli, along the lower half of the squamous portion of the 

 occipital bone from near the posterior margin of the foramen magnum to the 

 internal occif)ital protuberance. It usually begins in a right and a left branch, 

 known as the marginal sinuses. These proceed from the termination of each 



