688 THE CEREBRUM 



Visual perception and memory play an important part in all our 

 reactions. This is well shown by the fact that lesions of the occipital 

 region lead not only to hemianopia but also to psychical or cortical 

 blindness. The latter condition, however, is not always complete, 

 but may vary between a slight disturbance of our associations per- 

 taining to a certain number of visual sensations, and an absolute 

 inability on our part properly to recognize and rate all our visual impres- 

 sions. In some animals, for example, certain lesions may be produced 

 which permit sensations of sight as such to continue, while their ability 

 to recognize and properly associate these impressions is lost absolutely. 

 This constitutes true psychic blindness. 



In man, this condition which is known as word-blindness, was 

 first recognized in 1877 by Kussmaul.^ It is characterized by an 

 inability to comprehend printed or written words, without, however. 



Fig. 346. — Lateral View of a Human Hemisphere; Cortical Area V, Damage to 

 Which Produces "Mind-blindness" (Word-blindness); Cortical Area H, Damage 

 TO Which Produces "Mind-deafness" (Word-deafness); Cortical Area ;S, Dajviage 

 TO Which Causes the Loss of Audible Speech; Cortical Area W, Damage to Which 

 Abolishes the Power of Writing. (Donaldson.) 



involving the faculty of expressing our thoughts by words or in writing. 

 A person so afflicted is capable of seeing and even of copying the letters, 

 but he has no associations pertaining to them. For this reason, they 

 remain absolutely meaningless to him. He is, therefore, in the same 

 position as a person who attempts to read a language with which he is 

 not familiar, say Arabic or Chinese. The condition of word-blindness 

 forces us to assume that the psycho-optical region embraces a cir- 

 cumscribed area which is set aside for the perception and memory of 

 letters. As primitive man, in all probability, was not in possession 

 of an association zone of this kind, it has been developed in the course 

 of time. Its location has not been definitely established as yet, 

 although those cases of word-blindness which have come to autopsy, 

 have shown lesions in the second parietal convolution and gyrus 

 1 Storungen der Sprache, 1885. 



