180 PROCEEDINGS OF THE NATIONAL ^JiWSEUM. vol. xxxii. 



win^ of the sphenoid, 2 cm. laterad from the outer border of each 

 optic foramen (base of the anterior clinoid process). 



The line between aa and ajj runs near to the line of the internal 

 orbital sulcus of the brain and follows closel^^ the horizontal plane of 

 the base of the frontal lobe. 



Middle fossai; adults. — The anterior landmarks from which to meas- 

 ure (?««, ma^) are located at the anterior extremity of a line passing 

 vertically beneath the points «/>, aj). They correspond closely to the 

 point of the maximum forward bulge in the line of the middle foss^, 

 i. e. to the poles of the temporal lobes of the cerebrum. 



The posterior point {mp., m.p) is on the middle of the superior 

 border of the petrous part of each temporal bone (in the middle 

 between the distal end of that border at the tempo ro -parietal suture 

 and the medial extremity of the petrous wedge). The lines ma-mp 

 are suitable representatives of the antero-posterior diameter of the 

 temporal lobes of the brain. 



T\\Q posterior fossm consist each of a cerebral and a cerebellar por- 

 tion, both of which were measured. For anterior landmarks of both 

 portions in adults were chosen the points tnp. For the posterior land- 

 marks of the cerebellar parts of the cavity {pi, pi, Plate XV) 

 points were selected on the lower ridge of each lateral sinus, 1.5 cm. 

 from the median line, and the posterior points for the measurement of 

 the cerebral part {ps, ps) are 2.5 cm. vertically above a horizontal line 

 passing through the more superior of the, pi marks. 



The left inferior ridge of the lateral sinus and hence tire left^^ 

 point is in adult man very often lower than the right. In all such 

 cases it is sufficient for practical purposes to determine the location of 

 the vight 2)s point and place the left ps horizontally opposite, 1.5 cm. 

 from the median line. The median line is determined by extending 

 the long axis of the foramen magnum. 



The mp-pi line corresponds to the length of the superior plane of 

 the cerebellum; while the mp-ps line measures the length of that part 

 of the cerebrum which lies on the tentorium. The ps points corre- 

 spond quite closely to the occipital poles of the cerebrum. 



In the skulls of the human young and of various mammals, the 

 landmarks were virtually the same as in human adults, with the 

 distances between aa and aa and the points in the posterior fossa3 in 

 the smaller skulls diminished proportionatel}" according to the size of 

 the skull. 



Several additional measurements besides the foregoing were taken on 

 the ventral parts of the skulls and will be referred to later. 



No 'deformed, pathological, or in any way abnormal skull was 

 included in the series measured, and due care was exercised concerning 

 fortuitous variations affecting the landmarks. 



