printed letters of the alphabet, or words, signify certain sounds and certain articulatory movements. If the connection between the articulating or auditory centres, on the one hand, and the visual centres on the other, be ruptured,
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Fig. 15.—Scheme of the mechanism of vision, after Seguin. The cuneus convolution (Cu) of the right occipital lobe is supposed to be injured, and all the parts which lead to it are darkly shaded to show that they fail to exert their function. F. O. are the intra-hemispheric optical fibres. P. O. C. is the region of the lower optic centres (corpora geniculata and quadrigemina). T. O. D. is the right optic tract; C, the chiasma; F. L. D. are the fibres going to the lateral or temporal half T of the right retina; and F. C. S. are those going to the central or nasal half of the left retina. O. D. is the right, and O. S. the left eyeball. The rightward half of each is therefore blind: in other words, the right nasal field, R. N. F., and the left temporal field, L. T. F., have become invisible to the subject with the lesion at Cu.
we ought a priori to expect that the sight of words would fail to awaken the idea of their sound, or the movement for pronouncing them. We ought, in short, to have alexia, or inability to read: and this is just what we do have in many
