With this there goes another fact which characterizes this form of aphasia, and which is called Cortical, as opposed to the Subcortical Motor Aphasia described above, that the person may not be able even to think of the words which are appropriate to express his meaning.

This is the case when those persons who depend upon the memories of the movements of lip and tongue in their normal speech are injured as described.
Besides the two forms of Motor Aphasia now spoken of, there are certain other speech defects which are called Sensory Aphasia.

When a lesion occurs in one of the areas of the brain in the speech zone in which the requisite memories of words seen or heard have their seat--as when a ball player is struck over the sight centre in the back of the head--special forms of sensory aphasia show themselves.
The ball player will, in this case, have Visual Aphasia, being unable to speak in proportion as he is accustomed in his speaking to depend upon the images of written or printed words.

He is quite unable to read or write from a copy which he sees; but he may be able, nevertheless, to write from dictation, and also to repeat words which are spoken to him.

This is because in these latter performances he uses his auditory centre, and not the visual.