522 



THE VEINS OF THE HEAD AND NECK. 



opens into the straight sinus on reaching the anterior margin of the tentorium. It 

 receives branches from the falx, and sometimes from the mesial surface of the hemi- 

 spheres. 



The straight sinus (s. tentorii) (fig. -402, 2 3), continuous with the foregoing, 

 is also joined at its commencement by the vena magna Galeni from the interior of 

 the cerebrum. It runs backwards and downwards, along the junction of the falx 

 cerebri and the tentorium, to the internal occipital protuberance, where it is con- 

 nected by a cross branch, generally of small size, with the torcular Herophili, but is 

 mainly continued into the lateral sinus of the opposite side to that into which the 

 superior longitudinal sinus is prolonged. The straight sinus receives in its course 

 some superior cerebellar veins, and small branches from the tentorium. 



Fig. 404. INTERNAL VIEW OF 



THE BASE OF THE SKULL, 

 SHOWING THE SINUSES OF THE 

 DURA MATER, &C. (Allen 



Thomson. ) ^ 



The tentorium has been re- 

 moved, and also a small portion 

 of the roof of the orbit posteriorly 

 on the left side, so as to bring into 

 view the sinuses, which are laid 

 open, the arteries at the base of 

 the skull, and the trunks of the 

 cranial nerves. 



I, olfactory bulb ; II, optic 

 nerves ; HI, third nerve ; IV, 

 trochlear nerve ; V, placed oppo- 

 site to the middle of the three 

 divisions of the fifth nerve ; VI, 

 sixth nerve ; VII, facial and au- 

 ditory nerves ; VIII, placed oppo- 

 site to the glosso - pharyngeal, 

 pneumo-gastric and spinal acces- 

 sory nerves ; IX, hypoglossal 

 nerve ; 1, right internal carotid 

 artery as it makes its turn within 

 the cavernous sinus in the groove 

 of the sphenoid bone ; 2, its oph- 

 thalmic branch ; 3, right and left 

 posterior cerebral arteries, from 

 the former of which the posterior 

 communicating artery is seen 

 passing forwards to the internal 

 carotid ; 4, basilar artery ; 5, 

 vertebral arteries giving off the 

 anterior spinal ; x , middle menin- 



geal artery spreading upwards from the foramen spinosum ; 6, superior petrosal sinus ; 7, inferior 

 petrosal sinus ; 8, termination of the lateral sinus at the jugular foramen ; 8', commencement of the 

 lateral sinus ; 9, occipital sinus, in this case of large size ; 10, torcular Herophili, and below that 

 number in the figure, the superior longitudinal sinus. 



The lateral sinuses commence at the internal occipital protuberance, and 

 terminate on each side at the jugular foramen in the bulb of the internal jugular 

 vein. The sinuses of the two sides generally differ in size, the one into which the 

 superior longitudinal sinus is prolonged being much larger than that of the opposite 

 side, which is formed by a continuation of the straight sinus. Each sinus passes 

 outwards in the corresponding lateral groove of the occipital bone, forming an arch 

 with its convexity upwards, 1 and being lodged in the attached margin of the 

 tentorium, to the posterior inferior angle of the parietal bone, then curves down- 

 wards in the groove of the mastoid portion of the temporal bone, and finally turns 



1 A. E. Birmingham, Dublin Journal of Medical Science, February, 1891. 



