

THE SINUSES OF THE DURA 723 



The subcerebellar or inferior superficial cerebellar veins (vv. subcerebellares, w. 

 cerebelli inferiores), of large size, terminate :n the lateral, subpetrosal, and occipital 

 sinuses. 



The deep cerebellar veins bring blood from the interior of the cerebellum to 

 the superficial veins. 



Veins of the Pons. Veins come from the interior of the pons, the deep veins, 

 and empty into a plexus of superficial veins. From this superficial venous plexus 

 a superior vein passes to the bas'ilar vein, and an inferior vein either into a cerebellar 

 vein or. into the superpetrosal sinus. 



Veins of the Medulla Oblongata. Veins pass from the interior of the medulla 

 oblongata and end in a plexus on the surface. From this plexus comes an anterior 

 median vein, which is a prolongation of a like vein of the spinal cord a posterior 

 median vein corresponding to a like vein of the cord and small branches which 

 pass with the roots of the glossopharyngeal, vagus, spinal accessory, and hypo- 

 glossal nerves, and empty into the occipital and the subpetrosal sinuses. 



The perivascular lymph spaces are especially found in connection with the vessels of the 

 brain. These vessels are enclosed in a sheath, which acts as a lymphatic channel, through 

 which the lymph is carried to the subarachnoid and subdural spaces, from which it is returned 

 into the general circulation. 



The Sinuses of the Dura (Sinus Durae Matris) (Figs. 502, 503). 

 Ophthalmic Veins and Emissary Veins. 



The sinuses of the dura are venous channels which drain the blood from the 

 brain; they are situated between the two layers of the dura and are lined by 

 endothelium continuous with that which lines the veins. They are sixteen in 

 number, of which six are single and situated in the mesal plane; the other ten are 

 paired, five being placed on either side of the mesal plane. They are divided 

 into two sets: (1) Those situated at the upper and back part of the skull; (2) 

 those at the base of the skull. The former are : 



Superior sagittal sinus. Tentorial or straight sinus. 



Inferior sagittal sinus. Lateral sinuses. 



Occipital sinus. 



The superior sagittal sinus (sinus longitudinalis, sinus sagittalis superior (Figs. 

 502 and 503) occupies the attached margin of the falx cerebri. Commencing 

 at the foramen cecurQt^rough which it usually communicates by a small branch 

 with the veins of t'he nasal fossae, it runs from before backward, grooving the 

 inner surface of the frontal, the adjacent margins of the two parietals, and the 

 superior division of the crucial ridge of the occipital; near the internal occipital 

 protuberance it usually deviates toward the right, and is continued as the corre- 

 sponding lateral sinus. The sinus is triangular on transverse section, is narrow 

 in front, and gradually increases in size as it passes backward. Its inner surface 

 presents the internal openings of the superior cerebral veins, which run, for the 

 most part, from behind forward, and open chiefly at the back part of the sinus, 

 their orifices being concealed by valve-like folds; numerous fibrous bands, chordae 

 Willisii (Fig. 504), are also seen extending transversely across the inferior angle 

 of the sinus; and some small, white, projecting bodies, the glandulae Pacchioni 

 (granulationes arachnoidales}. This sinus communicates by numerous small 

 apertures with spaces in the dura known as lacunae laterales, or parasinoidal spaces 

 (Fig. 504). The arachnoid villi project into these spaces. The superior sagittal 

 sinus receives the superior cerebral veins, numerous veins from the diploe and 



