320 THE ANTIQUITY OF MAN 
Piltdown bones are surprisingly thick. The farm labourer 
who first saw the skull described it as a cocoanut. In 
most modern heads the thickness of the bones forming 
the brain chamber varies from 4 to 6 mm. (-J- to J of an 
inch) ; in native races, and occasionally in Europeans, 
the thickness may amount to 8 or even 10 mm., but in 
no normal modern skull are all the bones so uniformly 
thick as in this recently discovered specimen. As already 
pointed out, the ancient skulls found at Galley Hill, 
Clichy, and Olmo are thick, but not to the extent seen 
in the Piltdown fragments. Thickness is also a character 
of most Neanderthal skulls. In the Piltdown cranium the 
frontal, parietal, occipital, and temporal bones vary in thick- 
ness from 8 to 12 mm., the average all over being about 
•| of an inch. The bone is naturally formed ; there can 
be no question of disease. My collea2:ue, Mr Shattock, 
has definitely setded that point.^ There can be no 
doubt that sufficient of the skull has been recovered to 
provide us with the means of reaching a just and certain 
conclusion as regards the size and shape of that part of 
the head which contains the brain. Very few ancient 
skulls are so well represented as that of Piltdown. 
The discovery of almost a complete half — the right — of 
the lower jaw or mandible by Mr Dawson is a most 
fortunate circumstance (fig. 103). It lay in the iron- 
stained cemented stratum with unworn eoliths and the 
fragment of the tooth of an early Pliocene form of 
elephant. The importance of the mandible is at once 
apparent ; it provides us with the skeletal outline of 
the face of this ancient form of man. Each half of a 
human mandible consists of two distinct parts : (i) a 
horizontal part or body (fig. 103), which carries the 
teeth and forms the lower part of the outline of the 
face — from the angle of the jaw below the ear to the 
chin ; (2) a vertical part, which ascends from the angle 
to terminate in an ardcular knob or condyle. The 
socket — the glenoid cavity — for the articular knob is 
1 See Proc. Internat. Med. Congress, London, 1913 (Pathological 
Section). 
