THE BRAIN OF FOSSIL MAN 405 
we are in a position to apply our knowledge to casts 
taken from fossil skulls. It will be well, however, to 
have a clear idea of a simple and primitive brain, such as 
is seen in the highest of anthropoids — =-the gorilla. In 
fig. 146, I have set a profile drawing of the brain cast 
taken from the skull of a young gorilla on the same 
aspect of the cast of the Gibraltar skull — the smallest of 
the ancient h-uman skulls. Both were drawn on the 
same scale and poised on corresponding planes. The 
superimposition of the two drawings is an easy matter, 
for they have both the same general form — they are 
flattened as if the vault had been compressed towards the 
base. The fissure of Sylvius of the ape is laid over 
the same fissure of the human brain. The triangular 
hollow between the temporal lobe and the cerebellum, 
filled in life by the part of the temporal bone which 
contains the ear, is also superimposed. The super- 
imposition of these two drawings (fig. 146) shows us 
that in the evolution of the brain from a simian to a 
human stage all the lobes and convolutions were 
involved. There has been a general and extraordinary 
elaboration of all parts. The parietal lobe has been 
affected most ; the temporal lobe least. We know some- 
thing of the nature of the changes which have occurred. 
While enumerating the lobes of the brain, we noted that 
certain areas or centres were primary — the areas for -sight, 
hearing, common sensation — and that round the primary 
areas, association areas had arisen. It is the expansion 
and elaboration of these association areas — complex 
mechanisms built up of nerve cells and nerve fibres 
adjusted to serve definite purposes — which raises the 
human above the simian brain. In this expansion the 
simple arrangement of convolutions has been replaced by 
a more elaborate and complex one. In the last two 
months of foetal life the human brain passes from a stage 
in which the convolutions of the brain have a simple, 
somewhat anthropoid arrangement to the more complex 
human form. Even amongst modern people the degree 
to which the simple arrangement is replaced by the more 
