The Meninges of the Brain. 417 



half an inch above the auditory meatus, while the anterior 

 branch curves, with convexity forwards, to the anterior 

 inferior angle of the parietal bone, at which point, viz., 

 one and a half inches behind the external angular process 

 and one and a half inches above the zygoma, this artery 

 is usually wounded. The remaining portion of the an- 

 terior branch may be indicated by first establishing Reid's 

 base line which runs backwards from the lower border of 

 the orbit through the centre of the external auditory rnea- 

 tus. Having mapoed out Reid's base line, draw another 

 line from the external angular process of the frontal bone 

 parallel to it. Along this line measure off the distances of 

 one, one and a half, two, two and a half, inches. Through 

 these points draw lines at right angles to Reid's base line 

 from the upper border of the zygoma, and measure the 

 same distances up these vertical lines as they are distant 

 from the external angular process. Join the ends of these 

 vertical lines and the course of the main part of the an- 

 terior branch will be indicated. , 



Landmarks for Cerebral Sinuses. The longitudinal 

 sinus may be represented by a line extending from the gla- 

 bella, i.e., from the root of the nose, to the inion, or external 

 occipital protuberance. This line gradually increases from 

 one-quarter of an inch in width, in front, to half an inch 

 in width at the centre of the vertex. The lateral sinus is 

 divided into two parts, viz., the lateral sinus proper, or 

 transverse portion, behind, and the sigmoid portion in 

 front, and of these, the former corresponds to a line about 

 half an inch in width starting from the external occipital 

 protuberance and terminating at the asterion or parieto- 

 occipito-mastoid junction, situated one and a half inches 

 behind and three-quarters of an inch above the centre of 



