DIFFICULTIES OF RECONSTRUCTION 339 
of the brain and of the skull are fairly exact copies of 
each other. Symmetry is a primitive mark ; it is the 
most highly evolved — the most specialised — forms of 
human brains and heads which manifest asymmetrical 
conditions. A deformity of one or both sides of the 
head may be due to disease in life, or to earth-pressure 
after death, but no suggestion has ever been made that 
the asymmetry of the Piltdown skull was due to either 
of these causes. It was due, then, to either a high 
specialisation of the brain or to an error in reconstruc- 
tion. In either case it was important to discover an 
explanation of those peculiar features which I have just 
mentioned, for when we come to finally assign any being 
to its scale in humanity, it is not the mandible, the face, 
the teeth, or limbs which guide us, but the master organ 
of the human body — the brain. We cannot tell the 
shape and size of the brain until the various skull bones 
which form the brain case are rightly fitted in position. 
In fitting the parts of the skull together, we must 
begin at the hinder or occipital end of the head in this 
particular case, because the only fragment which reveals 
the middle line of the skull, and at the same time gives 
us a true indication of the width of the Piltdown head, 
belongs to the hinder aspect of the skull and forms part 
of the occipital bone. The aspect of the Piltdowi> head 
which we are to try and build up is exactly that seen in 
the person who sits in front of us in church or theatre. 
If the hair and soft covering parts were to become 
transparent we should see that the central part of the 
hinder wall of the skull is formed by the occipital bone 
(fig. 117). The lower or nuchal part of the bone is 
implanted in the neck, and gives attachment to those 
muscles which move the head. The nuchal part is 
shaded in fig. 117, so that it may be the more easily 
recogniseci. On either side of the occipital bone are 
placed the right and left temporal bones. In fact, the 
mastoid parts of the temporal form lateral extensions of 
the area for the attachment of the neck. The mastoid 
processes are in reality levers by which the muscles of the 
