20 A MANUAL OF ANATOMY. 



The junction of the vertical with the external surface of 

 a hemisphere is indicated by a line drawn from the nasion 

 over the top of the head to a point half an inch external 

 to the inion. 



This line when drawn on both sides will indicate the 

 position of the superior longitudinal sinus. 



The line of junction of the inferior and external surfaces 

 of the cerebrum is indicated as follows : 



Start the line at the nasofrontal groove, and carry it out- 

 ward to a point five-eighths of an inch (one-half to three- 

 fourths of an inch) above the E. A. P. ; from here pass 

 backward to the Sylvian point, then curve a line downward 

 and forward (with its concavity backward to correspond to 

 the rounded extremity of the temporal lobe) to a point just 

 above the junction of the zygoma with the frontal process 

 of the malar bone. (This last point is situated one-fourth 

 of an inch above the zygoma and the same distance from the 

 posterior border of the frontal process of the malar bone. 

 Or, if measured from the E. A. P., it is a vertical line 

 dropped downward from a point five-eighths of an inch 

 posterior to the E. A. P. to terminate one-fourth of an inch 

 from the zygoma.) Now continue the line backward and 

 slightly downward until the junction of the zygomatic arch 

 with the skull is reached (just over the condyle of the 

 inferior maxilla). The line then inclines upward and back- 

 ward to reach a point one inch behind and half an inch 

 above the level of the external auditory meatus. (This 

 portion of the line passes from one-eighth to three-eighths 

 of an inch above the upper margin of the external meatus 

 and intersects a vertical line drawn upward from the pos- 

 terior border of the root of the mastoid process, one inch 

 behind and half an inch above the external auditory meatus.) 



The lower posterior border of the cerebrum is finished 



