I502 



A MANUAL OF ANATOMY 



The convexity of the genu of the sigmoid sinus is on a level with 

 the temporo-mandibular joint, and lies from | to J inch behind the 

 base of the suprameatal triangle, or | inch behind the pre-auricular 

 point. 



The right sigmoid sinus is usually larger than the left. In many 

 cases the genu is scarcely perceptible, and the horizontal and vertical 

 limbs under these circumstances are practically almost in direct 

 continuity with each other. The genu lies at a depth from the 

 surface varying from | to | inch. 



Fig. 623. — Diagram showing the Relations of the Chief Cerebral 

 Fissures to the Exterior of the Head (Reid). 



B.C. Transverse Fissure 

 D.E., F.G. Reid's Perpendicular Lines 

 Sy. Fis. Sylvian Fissure 

 Sy.a. Fis. Anterior Limb of .Sylvian Fissure 

 Sy.h.Fis. Posterior Horizontal Limb of 

 Sylvian Fissure 

 p.o.Fis. External Parieto-occipital Fissure 

 + Parietal Eminence 



A. Glabella 



B. Inion 



C Auricular Point 



E. Pre-auricular Point 



F. .Superior Rolandic Point 



G. Posterior Border of Root of Mastoid 



Process 

 H. Inferior Rolandic Point 



The middle meningaal artery corresponds to the centre o4 the 

 zygomatic arch. At a point from i to J inch above the centre of 

 the arch it divides into its two terminal branches— anterior and 

 posterior. 



The large anterior division of the middle meningeal artery, as it 

 lies in the groove, or, it may be, short canal, on the internal aspect 

 of the antero-inferior angle of the parietal bone, is indicated by 

 taking a point i^ inches behind the external angular process of the 

 frontal bone, and i^ inches above the zygomatic arch. From this 



