iS-l 



YEIXS OF THE HEAD AND NECK. 



the dura mater converge to a common point, -^-hich corresponds -u-ith 

 the internal occi[)ital protnberance, and is called the confluence of 

 the sinuses or torcular Herophili. The form of the torcular is very 

 irregular. Five or six apertures open into it : viz., one from the longi- 

 tudinal, and one from the straight sinus ; two from the right and left 

 lateral sinuses ; and one or tvro from the posterior occipital sinuses. 



Fig. 306. 



Fig. 306. — Sketch op the In- 

 ternal Veins of the Cranium 

 AND Nose. J 



«, torcular Heropliili ; b, su- 

 perior longitudinal sinus of the 

 dura mater ; c, inferior longitudinal 

 sinus ; d, straight sinus ; e, in- 

 ternal veins of the brain, or veins 

 of Galen ; ff, occipital sinus ; /;, 

 superior petrosal sinus ; {, inferior 

 petrosal sinus ; I; nasal veins on the 

 septum : some of which superiorly 

 form the commencement of the 

 superior longitudinal sinus, and 

 others lower down pass out by the 

 spheno-palatine foramen. 



The superior longitu- 

 dinal sinus (s. falciformis 

 superior), commencing at the crista galli, extends from before backwards, 

 in tlie upper border of the falx cerebri, graduallv increasing in size as 

 it proceeds. It is three-sided, and is crossed obliquely at the inferior 

 angle by several bands, the chonlce WiUisii. The veins from the cerebral 

 surface open into this sinus chiefly towards the back part ; and in such 

 a way that the apertures of the greater number of them are directed 

 from behind forwards, contrary to the direction of the current within 

 it. The longitudinal sinus communicates with the veins on the out- 

 side of the occipital bone, by a branch (one of the *' emissary veins," 

 Santorini) which passes through a hole in the parietal bone. 



Tlie inferior longitudinal sinus (s. falciformis inferior) is very 

 small, and has so much of a cylindrical form, that it is sometimes 

 named inferior ionfiihuUaal vein. Placed in the inferior concave border 

 of the falx cerebri, it runs from before backwards, and opens into the 

 straight sinus on reaching the anterior margin of the tentorium cere- 

 belli. It receives branches from the surface of the falx cerebri, and 

 sometimes from the flat surface of the hemispheres. 



The straight sinus (s. tentorii) runs backwards in the base of the 

 falx cerebri, gradually widening as it approaches the torcular 

 Herophili, in which it terminates. Besides the inferior longitudinal 

 sinus, the venre Galeni and the superior veins of the cerebellum open 

 into it. 



The lateral sinuses (s. transversi) are of considerable size. Their 

 direction conforms to that of the groove marked along the inner sur- 

 face of the occipital and other bones, and extending from opposite the 

 internal occipital protuberance to the foramen jugulare. The sinus of 

 the right side is usually larger than that of the left ; both commence at 

 the torcular Herophili, and terminate in the jugular veins. The lateral 

 -sinuses receive the blood transmitted from both the longitudinal sinuses, 



