sight altogether.[1] Recent pathological annals seem to offer a few such cases.[2] Meanwhile there are a number of cases of mental blindness, especially for written language, coupled with hemianopsia, usually of the rightward field of view. These are all explicable by the breaking down, through disease, of the connecting tracts between the occipital lobes and other parts of the brain, especially those which go to the centres for speech in the frontal and temporal regions of the left hemisphere. They are to be classed among disturbances of conduction or of association; and nowhere can I find any fact which should force us to believe that optical images need[3] be lost in mental blindness, or that the cerebral centres for such images are locally distinct from those for direct sensations from the eyes.[4]
Where an object fails to be recognized by sight, it often happens that the patient will recognize and name it as soon as he touches it with his hand. This shows in an interest-
- ↑ Nothnagel (loc. cit. p. 23) says: "Dies trifft aber nicht zu." He gives, however, no case in support of his opinion that double-sided cortical lesion may make one stone-blind and yet not destroy one's visual images; so that I do not know whether it is an observation of fact or an a priori assumption.
- ↑ In a case published by C. S. Freund: Archiv f. Psychiatrie, vol. XX, the occipital lobes were injured, but their cortex was not destroyed, on both sides. There was still vision. Cf. pp. 291–5.
- ↑ I say 'need,' for I do not of course deny the possible coexistence of the two symptoms. Many a brain-lesion might block optical associations and at the same time impair optical imagination, without entirely stopping vision. Such a case seems to have been the remarkable one from Charcot which I shall give rather fully in the chapter on Imagination.
- ↑ Freund (in the article cited above 'Ueber optische Aphasie und Seelenblindheit') and Bruns ('Ein Fall von Alexie,' etc., in the Neurologisches Centralblatt for 1888, pp. 581, 509) explain their cases by broken-down conduction. Wilbrand, whose painstaking monograph on mental blindness was referred to a moment ago, gives none but a priori reasons for his belief that the optical 'Erinnerungsfeld' must be locally distinct from the Wahrnehmungsfeld (cf. pp. 84, 93). The a priori reasons are really the other way. Mauthner ('Gehirn u. Auge' (1881), p. 487 ff.) tries to show that the 'mental blindness' of Munk's dogs and apes after occipital mutilation was not such, but real dimness of sight. The best case of mental blindness yet reported is that by Lissauer, as below. The reader will also do well to read Bernard: De l'Aphasie (1885) chap, V; Ballet: Le Langage Intérieur (1886), chap, VIII; and Jas. Ross's little book on Aphasia (1887), p. 74.
