264 THE ANTIQUITY OF MAN 
to the Java fragment. The base line is that shown 
in many of the illustrations in this book (see fig. 72). 
Even when such a base line is used we meet with 
a difficulty. Our base line crosses the hinder lower 
angle of the parietal bone. That angle is present in the 
calvaria of Pithecanthropus, and can be utilised (fig. 90). 
In front the zero line should cross the fronto-malar 
junction, but, as will be seen in fig. 90, this line is made 
to pass nearly 10 mm. below this junction. The line is 
placed at such a low position because the fronto-malar 
junction in anthropoid skulls is situated much higher, as 
regards the floor of the brain cavity, than in human skulls. 
This point will be again discussed when we come to deal 
with the Piltdown skull (see p. 380). It is sufficient at 
present to draw attention to the fact that the bones 
forming the side of the skull behind the fronto-malar 
junction, the frontal and sphenoid (fig. 90), are disposed, 
not as in human skulls, but as in those of anthropoids (see 
fig. 138, p. 382). That is an important fact in fixing the 
position of Pithecanthropus in the scale of human evolu- 
tion. In the fronto-malar region of the Java skull all 
the anthropoid traits are retained. 
The importance of the height of the vault of the skull 
above this zero line (fig. 90) is readily understood. As 
the brain grows in size and complexity, the extra room 
required is obtained — as Professor Arthur Thomson 
clearly demonstrated fifteen years ago ^ — by the expansion 
of the roof and sideSo The vault rises above the base 
line as the brain grows. In average skulls of the modern 
type the vault rises about 100 mm. above this standard 
line ; in the Gibraltar skull — the lowest pitched of all 
Neanderthal skulls — the vault rises to 86 mm. above 
the zero line, but in Pithecanthropus the height is only 
74 mm. (fig. 91). In the great anthropoids — the orang, 
chimpanzee, and gorilla — the height of the cranial vault 
varies from 50 to 60 mm. above the base line. Thus in 
height of crania] vault Pithecanthropus is rather nearer to 
' "On Man's Cranial Form," Proc. of Internat. Medical Congress, 
Madrid, 1903. 
