by the hands of E. Hitzig and
D. Ferrier and their followers has slowly succeeded in obtaining certain
facts about the _cortex cerebri_ which not only show that different
regions of it are concerned with different functions, but, for some
regions at least, outline to some extent the kind of function exercised.
It is true that the greater part of the cortex remains still _terra
incognita_ unless we are content with mere descriptive features
concerning its coarse anatomy. For several scattered regions some
knowledge of their function has been gained by physiological
investigation. These scattered regions are the _visual_, the _auditory_,
the _olfactory_ and the _precentral_.

The grey matter of the cerebral cortex is broadly characterized
histologically by the perikarya (nerve-cells bodies) which lie in it
possessing a special shape; they are pyramidal. The dendrite fibres of
these cells--that is, their fibres which conduct _towards_ the
perikarya--are branches from the apex and corners of the pyramid. From
the base often near its middle arises one large fibre--the axone fibre,
which conducts impulses away from the perikaryon. The general appearance
and arrangement of the neurones in a particle of cortical grey matter
are shown in fig. 15, above. The apices of the pyramidal perikarya are
turned towards the free surface of the cortex. The figure as interpreted
in terms of functional conduction means that the cortex is beset with
conductors, each of which collects nerve-impulses, from a minute but
relatively wide field by its branched dendrites, and that these
nerve-impulses converge through its perikaryon, issue by its axone, and
are carried whithersoever the axone runs. In some few cells the axone
breaks up into branches in the immediate neighbourhood of its own
perikaryon in the cortex. In most cases, however, the axone runs off
into the subjacent white matter, leaving the cortex altogether. On
reaching the subjacent white matter it mingles with other fibres and
takes one of the following courses:--(1) to the grey matter of the
cortex of the same hemisphere, (2) to the grey matter of the cortex of
the opposite hemisphere, (3) to the grey matter of the pons, (4) to the
grey matter of the bulb or spinal cord. It is noteworthy that the
dendrite fibres of these cortical neurones do not transgress the limits
of the grey cortex and the immediate neighbourhood of the perikaryon to
which they belong; whereas the discharging or