by this bridge.

[Illustration: Fig. 16]

[Description: FIG. 16.--Diagram of the left hemisphere of the brain showing
localised centres, of which the functions are known. It will be observed
that the centres for the special senses, tactile, muscular, hearing, and
vision, are all situated behind the central fissure. The tactile-motor
kinæsthetic sense occupies the whole of the post-central convolution; the
centre for hearing (and in the left hemisphere memory of words) is shown at
the end of the first temporal convolution, but the portion shaded by no
means indicates the whole of the grey cortex which possesses this function;
a large portion of this centre cannot be seen because it lies within the
fissure forming the upper surface of the temporal lobe. Behind this is the
angular gyrus which is connected with visual word memory. The half-vision
centre, and by this is meant the portion of brain which receives
impressions from each half of the field of vision, is situated for the most
part on the inner (unseen) surface of the occipital lobe. In front of the
central fissure is situated the motor area, or that region destruction of
which causes paralysis of the muscles moving the structures of the opposite
half of the body. If the situations indicated by black dots be excited by
an interrupted electric current, movements of the limbs, trunk, and face
occur in the precise order shown, from the great toe to the larynx. In
front of this precentral convolution are the three frontal convolutions,
and it would seem that the functions of these convolutions are higher
movements and attention in fixation of the eyes; moreover, in the lowest
frontal region, indicated by fine dots, we have Broca's convolution, which
is associated with motor speech; above at the base of the second middle
frontal convolution is the portion of cortex in which is localised the
function of writing. Taste and smell functions reside in brain cortex only