462 



VEINS OF THE HEAD AND NECK. 



two sets, viz., those placed in the prominent folds of the dura mater, and 

 those situated in the base of the skull. 



Fig. 313. 



Fig. 313. SKETCH OP THE IN- 

 TERNAL VEIKS OP THE CKANIDSI 

 AND NOSE. 



a, torcular Herophili ; J, superior 

 longitudinal sinus of the dura mater ; 

 c, inferior longitudinal sinus ; d, 

 straight sinus ; e, internal veins of 

 the brain, or veins of Galen ; g, occi- 

 pital sinus ; h, superior petrosal 

 sinus ; i, inferior petrosal sinus ; k, 

 nasal veins on the septum ; superiorly 

 is shown the commencement from 

 soni3 of these of the superior longi- 

 tudinal sinus, and lower down some 

 of the nasal veins passing out by the 

 spheno-palatine foramen. 



The form and size of the 

 sinuses are various. All of 

 them are lined by a con- 

 tinuation of the internal mem- 

 brane of the veius, the dura mater serving as a substitute for the other coats. 



The sinuses which are contained in the several processes or folds of the 

 dura mater converge to a common point, which corresponds with the internal 

 occipital protuberance, 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 longitudinal, and one from the straight 

 sinus ; two from the right and left lateral sinuses ; and one or two from 

 the posterior occipital sinuses. 



The superior longitudinal sinus (s. falciformis superior), commencing at the 

 crista galli, extends from before backwards, in the upper border of the falx 

 eerebri, gradually increasing in size as it proceeds. It is three-sided, and 

 is crossed obliquely at the inferior angle by several bands, the chordce TFillisii. 

 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 outside of the occipital bone, by a branch (one of the "emissary veins," 

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



The inferior longitudinal sinus (s. falciformis inferior) is very small, and 

 so much resembles a cylindrical vein, that it is sometimes named inferior 

 longitudinal 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 teiitorium cerebelli. It receives branches from 

 the surface of the falx cerebri, and sometimes from the flat surface of the 

 hemispheres. 



The straight sinus (s. quartus ; 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 venae 

 Galeni and the superior veins of the cerebellum open into it. 



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

 tion conforms to that of the groove marked along the inner surface of the 

 occipital and other bones, and extending from opposite the internal occi- 



