DESCRIPTION OF THE FRONTISPIECE 



The upper figure is from a cast of the celebrated specimen found 

 in a river gravel in Java, probably of as great age as the palaeolithic 

 gravels of Europe. Though rightly to be regarded as a ' man 'the 

 creature which possessed this skull has been given the name 'Pithecan- 

 thropus.' The shape of the cranial dome differs from that of a well- 

 developed European human skull (shewn in the lower photograph, that of 

 a Greek skull) in the same features as do the very ancient prehistoric 

 skulls from the Belgian caves of Spey, and from the Neanderthal of the 

 Rhineland. These differences are, however, measurably greater in the 

 Javanese skull. 



The three great features of difference are: (i) the great size of the 

 eye-brow ridges (the part below and in front of A in the figures) in the 

 Java skull ; (2) the much greater relative height of the middle and back 

 part of the cranial dome (lines e and /) in the Greek skull ; (3) the much 

 greater prominence in the Greek skull of the front part of the cranial dome 

 the prefrontal area or frontal ' boss ' (the part in front of the line A C, 

 the depth ^Df which is shewn by the line d). 



The parts of the cranial cavity thus obviously more capacious in the 

 Greek skull are precisely those which are small in the Apes and overlie 

 those convolutions of the brain which have been specially developed in 

 Man as compared with the highest Apes. 



The line AB in both the figures is the ophryo-tentorial line. It is 

 drawn from the ophryon (the mid-point in the line drawn across the 

 narrowest part of the frontal bone just above the eye-brow ridges), which 

 corresponds externally to the most anterior limit of the brain, to the 

 extra- tentorial point (between the occipital ridges) and is practically the 

 base line of the cerebrum. The lines e and /are perpendiculars on this 

 base line, the first half-way between A and B, the second half-way between 

 the first and the extra-tentorial point. 



C is the point known to craniologists as ' bregma,' the meeting point of 

 the frontal and the two parietal bones. 



The line A C is drawn as a straight line joining A and C but if the 

 skull is accurately posed it corresponds to the edge of the plane at right 

 angles to the sagittal plane of the skull which traverses both bregma (C) 

 and ophryon (A) and where it ' cuts ' the skull marks off the prefrontal 

 area or boss. (See for the full-face view of this area in the two skulls Figs, i 

 and 2.) The line d is a perpendicular let fall from the point of greatest 

 prominence of the prefrontal area on to the prefrontal plane. It indicates 

 the depth of the prefrontal cerebral region. Drawn on both sides on the 

 surface of the bone and looked at from in front (the white dotted line in 

 Figs, i and 2) it gives the maximum breadth of the prefrontal area. 



By dividing the ophryo-tentorial line into 100 units, and using those 

 units as measures, the depths of the brain cavity in the regions plumbed 

 by the lines d, e, and /, can be expressed numerically and their differences 

 in a series of skulls stated in percentage of the ophryo-tentorial length. 



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