as moving objects. It saw
them perhaps as things to which mental association gave no significance.
Similarly, a dog after ablation of the occipital lobes of the cortex is
able to see, for it avoids obstacles in its path; but if food is offered
to it or the whip held up to it, it does not turn towards the food or
away from the whip. It sees these things as if it saw them for the first
time, but without curiosity, and as if it had no experience of their
meaning. It gives no hint that it any longer understands the meaning of
even familiar objects so long as these are presented to it through the
sense of vision. Destruction of the visual cortex of one hemisphere
alone produces in the dog impairment of vision, not as in the bird
practically exclusively in the opposite eye, but in one lateral half of
each eye, and that half the half opposite the hemisphere injured. Thus
when the cortex destroyed is of the right cerebral hemisphere, the
resultant visual defect is in the left half of the field of vision of
both eyes. And this is so in man also.

In man disturbances of sensation can be better studied because it is
possible to obtain from him his description of his condition. The
relation of the _cortex cerebri_ to human vision can be summarized
briefly as follows. The visual cortex is distinguishable in higher
mammals by a thin white stripe, the stripe of Gennari, seen in its grey
matter when that is sectioned. This stripe results from a layer of
nerve-fibres, many of which are axones from the neurones of the lateral
geniculate body and the pulvinar, the grey masses directly connected
with the optic nerve-fibres. In the dog, and in such monkeys as the
Macaque, the region of cortex containing this stripe traceable to optic
fibres forms practically the whole occipital lobe. But in the man-like
apes and in man this kind of cortex is confined to one region of the
occipital lobe, namely, that of the calcarine fissure and the _cuneus_
behind that. This region of cortex thus delimited in man is one of
Flechsig's areas of earlier myelinization. It is also one of his areas
possessing projection fibres; and this last fact agrees with the
yielding by this area, when under electrical stimulation, of movements
indicating that impulses have been discharged from it into the motor
neurones of the muscles of the eyes and neck. Evidence from cases of
disease show that destruction of the cortex of the upper lip of the
calcarine fissure, say in the