cortical area than has
closure of the jaws. It is interesting that certain agents, for instance
strychnine, and the poison of the bacilli which cause the disease known
as tetanus or lock-jaw, upset this normal topography, and replace in the
cortex flexion of the limb by extension of the limb, and opening of the
jaw by closure of the jaw. There is, however, no evidence that they do
this by changing in any way the cortical mechanisms themselves. It is
more likely that their action is confined to the lower centres, bulbar
and spinal, upon which the discharge excited from the cortex plays. The
change thus induced in the movement excited by the cortex does, however,
show that the point of cortex which causes for instance opening of the
mouth is connected with the motor nerves to the closing muscles as well
as with those of the opening muscles. This is an item of evidence that
the "centres" of the cortex are connected with the motor nerves of
antagonistic muscles in such a way that when the "centre" excites one
set of the muscles to contract, it simultaneously under normal
circumstances causes inhibition of the motor neurones of the opposed set
of muscles (reciprocal innervation). In the great majority of movements
excited from the motor cortex of a single hemisphere of the cerebrum,
the movement evoked is confined to one side of the body, namely to that
opposite to the hemisphere stimulated. There are, however, important
exceptions to this. Thus, adduction of both vocal cords is excited from
the cortex of either hemisphere. The movement of closure of the eyelids
is usually bilateral, unless the stimulation be very weak; then the
movement is of the eyelids of the opposite side only. The same holds
true for the movements of the jaw. It, therefore, seems clear that with
many movements which are usually bilaterally performed in ordinary life,
such as opening of the jaw, blinking, &c., the symmetrical areas of the
motor regions of both hemispheres are simultaneously in action.

In regard to all these movements elicitable by artificial stimuli from
the motor cortex it is obvious that were there clearer evidence that the
pallial region from which they are elicitable is fairly directly
connected with corticopetal paths subserving cutaneous sensation or
"muscular sense," the movements might be regarded as falling into the
category of higher reflexes connected with the organs of touch, muscular
sense, &c., just as the movements of the