1277 
that of a 2 orang utan 32 mm., of a £ Hylobates agilis and of a 
J Siamang 5 mm., of a g Semnopithecus entellus 14 mm., and of 
a & Macacus cynomologus 18 mm. above the right sulcus transversus. 
But in this way the great height of the lower part of the skull 
in the Neandertal type can only be accounted for for about a third 
part, and there exists a considerable difference in the relative height 
of the lower part of the skull between the two Hylobatides, though 
the inion is situated at the same distance above the sulcus trans- 
versus. It should be pointed out here that the platycephaly of the 
Siamang is by no means to be explained by the greater size of its 
body, for its weight is only the half more than that of the smaller 
Hylobatides. In the development of the brain they are certainly all 
about on a line, and yet the skull of the Siamang is in comparison 
with the other Hylobatides as much flattened as that of the Nean- 
dertal Man in comparison with recent Man (Fig. 1 and Fig. 2). 
It may, therefore, be assumed that the homologous lower part of 
the skull in relation to the whole is more capacious in Homo nean- 
dertalensis than in Homo sapiens, not or not chiefly on account of 
the upper part of the brain being less large in itself, but in con- 
sequence of similar external causes as make the lower part more 
spacious in the platycephalic Siamang than in his smaller relative. 
Also in the skull of the Neandertal Man the flattening above must 
have caused part of the brain to be displaced downward.In fact for the 
physiological function of the brain the place which it occupies in 
the skull is very indifferent; it is not so with the bone- and 
muscle substance at the skull, whose funetion is directly dependent 
on the place. This leads to the insight that the peculiar shape of 
the skull of the Neandertal type was not determined, at least not - 
chiefly, by the comparatively small size and low stage of develop- 
ment of the encephalon, but by external mechanic factors, chiefly 
in connection with the position and poise of the skull on the spinal 
column — which I have referred in my communication of September 
25, 1920 on the “Protoaustralian Fossil Man of Wadjak, Java’? — 
just as the platycephaly in the Siamang, in contrast to the other 
Hylobatides, can only be explained by its comparatively large jaws. 
The capacity of the skull of 1288 cm.* to be calculated for the 
man of the Neander-valley from the calvaria, in accordance with 
the proportion in the recent human type, must then be much too 
small. According to the ratio which exists in Apes between the 
calvaria and the total capacity of the skull this fossil man would 
have possessed a brain capacity of 1472 em*. Bourn’) calculated 
1) M. Boure, L'Homme fossile de La Chapelle-aux-Saints, p. 189. 
