588 TRANSACTIONS OF SECTION H. 
better in the New World Apes; but they became well developed in the Old 
World Apes, and very highly skilled and controlled in all the Anthropoid Apes. 
It was this gradual increase in skill of hand and arm which made it advantageous 
for the ancestors of the Gibbon to adopt, more definitely than Z'arsius had done, 
the preet BuaAe and for their structure to become ‘set’ to make the best use of 
such skill, 
But, marked as are the changes that can be detected in the behaviour of the 
erect Gibbon, in the increased size and specialisation of its motor and prefrontal 
areas, of which the latter is an expression of an improved control over the func- 
tions of the cortex as a whole, there is a significant increase in the size of the 
area which intervenes between the -visual, tactile, and auditory centres. The 
growth and increased functional value of this parietal area, which from its 
position is obviously the place for storing the records of the complex states of 
consciousness, blended of visual, tactile, and auditory sensations, lie at the root 
of all the other changes in the brain; and the perfecting of the mechanism for 
supplying consciousness with these more perfect materials of experience, explains 
the increased ability to perform more highly skilled movements which, in turn, 
led to the adoption of the erect attitude, and thus freed the hands for the work 
they had for the first time become skilled to perform. 
So far in this address I have been attempting to sketch certain outstanding 
features of Man’s ancestry with the object of offering some explanation of the 
factors which made possible the emergence of such a creature as Man. We have 
seen that the adoption of an arboreal life by some small Insectivore-like creature, 
shortly before the dawn of the Tertiary period, and its subsequent cultivation 
of the sense of vision until it became a highly specialised Anaptomorphid, enabled 
Man’s remotest Primate ancestor to escape from the domination of the sense of 
smell as the guiding influence of its lite, and to cultivate its other senses, so as 
immensely to widen the sensory avenues by which the outside world could affect 
its conscious activities. The arboreal life, which demanded great activity and 
agility, led to the special cultivation of skilled movements of the limbs, and 
such an acquirement was clearly facilitated in this group by the perfection of 
visual control, without which finely adjusted actions of the hands and feet 
could not easily be learned. The acquisition of such skill in movement necessi- 
tated the increased perfection of the tactile and other sensory areas of the brain, 
so as the more nicely to control the adjustments and correlations of muscles 
essential for any precise action. Thus, we have a chain of linked influences that 
follow on the specialisation of the visual apparatus in the brain of our primitive 
arboreal ancestor—the perfecting of touch and the acquirement of skill in 
action. ‘The heightened acuity of vision and the expansion of the cortical area 
for storing visual impressions, together with the growing importance of touch, 
and in a less measure, perhaps, of hearing, immensely widened the psychical 
content of the life of the Eocene Tarsioid in comparison with that of its con- 
temporaries; but there is yet another factor which its mode of life called into 
play which was fraught with the most far-reaching possibilities in the creation 
of Man. The co-ordination of large groups of muscles for the purpose of per- 
forming some precise action, which must be controlled during the stage of learn- 
ing by tactile, kinesthetic and visual impressions and memories—the fruits of 
experience—necessitated the formation of some cortical apparatus which would 
control and harmonise the activities of the various centres, regulating the 
muscular actions, and bringing the total sum of consciousness at any one moment 
to bear upon the performance of a given act. Out of such a necessity as this 
there sprang in the early ancestor of Man—and, though in much less degree, in 
certain other phyla also—an outgrowth of the motor cortex, which became the 
mechanism for attention and the orderly regulation of the psychical processes. 
Thus, at the very dawn of the Tertiary period there were developed the 
germs of all the psychical greatness which, in the million or so of years that have 
followed, culminated in the human mind. 
But the early Primate stem attained this distinctive position of relative 
isolation, not merely by the development of its own members, but also by the 
rapid and divergent specialisation of other mammalian groups. The enhanced 
plasticity conferred upon mammals by the development of a neopallial cortex, 
which enabled them to exercise, to an immeasurably greater degree than any of 
their predecessors had enjoyed, what we may without inaccuracy term intelligent 
