Other relations of interest are the apex of the temporal lobe, a little beneath the line (2-2) and at about 10 to 15 mm. posterior to the external angular process of the frontal bone; the situation of the occipito-parietal fissure, almost immediately under the posterior end of the line (2-2) at its junction with the lines (E E), which indicate the posterior extremity of the cerebrum; the anterior end of the brain being marked off by the line (D D). {96} Furthermore, for certain purposes the limits of the basal or central ganglia may be estimated as follows: Their superior limit is indicated by a horizontal line (3-3) drawn at 45 mm. below the vertex, their anterior limit corresponding to the head of the nucleus caudatus by the vertical line (C C), and their posterior limit, the hinder end of the thalamus, by the vertical line (B B). Upon the median line at the top of the head an allowance of full 15 mm. should be made for the width of the superior longitudinal sinus separating the hemisphere. [Illustration: FIG. 14. The same Topographical Lines applied to the Left Cerebral Hemisphere in Henle's Skull. The motor centres are approximately indicated by dotted lines. (The leg centre should be reduced in size as it lies near to and in the longitudinal fissure.) The Rolandic line is placed a little behind the fissure for the sake of clearness.] The location of the middle meningeal artery, which so often furnishes the blood that compresses the brain after various injuries to the head, is surgically of great importance. The course of its two principal branches is approximately indicated upon Fig. 13 by the branching lines drawn on the anterior inferior angle of the parietal and the upper part of the squamous portion of the temporal bone. In the living subject the main trunk of the artery would be found under the horizontal line (2-2) a little posterior to the speech-centre, about 30 mm. behind the external angular process, and in front of the beginning of the fissure of Sylvius. Upon the shaven head of a patient seated in a chair or lying in bed the principal landmarks and relations above defined can be mapped out with sufficient approximation to accuracy by the use of a ruler to mark {97} the alveolo-condyloid plane, and a cardboard cut so as to stand astride the head in the auriculo-bregmatic vertical. A light wooden apparatus can easily be made to indicate these two lines, while the remaining measurements can be made with a steel tape-measure, and the points marked with carmine ink or an aniline pencil.