Chap, in.] CRANIAL CONTENTS. 35 



The fissure of Rolando is some way behind the 

 coronal suture. 



The temporo-sphenoidal lobe lies almost wholly 

 below a line drawn horizontally backwards from the 

 external angular process. The upper borders of the 

 optic thalamus and corpus striatum are about on a 

 level with the top of the pinna. They are situate 

 opposite the temporal region, and the anterior limit 

 of the corpus striatum about corresponds to the 

 pterion. 



The following more detailed account of the topo- 

 graphy of the brain is given by Dr. Reid. 



The base line, from which all perpendicular 

 lines are drawn, runs through the lowest part of the 

 infraorbital margin and the middle of the external 

 auditory meatus. 



Longitudinal fissure of cerebrum. A line running 

 along the median line of the top of the head from the 

 root of the nose to the occipital protuberance. 



Transverse fissure. A line from the occipital 

 protuberance to the external auditory meatus. 



Fissure of Sylvius. A line from a point 1 

 inches behind the external angular process P to a 

 point f of an inch below the most prominent part of the 

 parietal eminence x. The first of an inch of the 

 line will represent the main fissure, and the rest of 

 the line will indicate the horizontal limb. The 

 ascending limb will start from the posterior end of 

 the line indicating the main fissure, and run vertically 

 upwards for about one inch. 



Fissure of Rolando. From the base line draw 

 two vertical lines upwards, one A B from the de- 

 pression in front of the meatus, and another c D 

 from the posterior border of the mastoid process at 

 its root. There is thus formed a four-sided figure, 

 bounded above and belov by the lines of the longi- 

 tudinal fissure and the horizontal limb of the Sylvian 



