PHYSIOLOGICAL TOPOGRAPHY OF SURFACE OF CEREBRUM. 799 



Exclusive irritation of the color-center gives rise to the appearance of color- 

 hallucinations, as observed in the colored aura in cases of epilepsy. Colored 

 vision occurs also in conjunction with other cerebral affections, for example as 

 erythropia. Rarely, the subject has observed everything as yellow, or blue, or 

 violet. Some poisons give rise to the same result through an influence upon the 

 cerebral color-center: yellow vision due to santonin, red vision due to henbane, 

 violet vision due to hashish. Lesions of the color-center have been found as the 

 result of cerebral concussion and after the action of various poisons, permanent 

 or transitory, total or partial color-blindness resulting. 



The remaining portion of the center contains the optical memory- 

 field, destruction of which gives rise to mind-blindness, in case of a lesion 

 on one side especially upon the contralateral side. A special form of 

 this condition is known as word-blindness, the individual no longer recog- 

 nizing the symbols of writing alexia. The area comprises, according 

 to Flechsig, the supramarginal gyms and the parietal lobule. Figures 

 and letters appear to have special central memory-fields. 



An interesting case of mind-blindness may be cited. After severe emotional 

 disturbance loss of the memory of visual perceptions developed suddenly in an 

 intelligent man. Everything with which he had been familiar persons, streets, 

 houses appeared entirely strange to him and he even no longer recognized his 

 image in the mirror. On attempting to read or figure he was compelled to speak 

 the words and figures aloud. In his dreams visual images were entirely wanting. 



In consequence of morbid irritation of the visual center, pronounced visual 

 hallucination may develop in man, principally in the insane. Famous instances 

 of visual hallucination are furnished by Jeanne dArc, Cardanus, Swedenborg, 

 Nicolai, Justinus Kerner, Holderlin. "The spirit and the demons of all time, 

 the divine vision of the ascetics" inanition-hallucinations in fasting persons 

 "the spiritual representation of the magician, the dream-object and the hallu- 

 cination of the febrile and insane patient are one and the same phenomenon" 

 (Johannes Muller). Cases have also been observed in which hallucinations were 

 present only in one eye. Occasionally, these are seen, for example, in cases of 

 delirium tremens, principally without color, therefore gray. 



After degeneration of the cortical center, in the first and second occipital 

 convolutions, cuneus and lingual lobe, the fibers degenerate that connect the 

 occipital lobe with the external geniculate body, the anterior quadrigeminate 

 body and the pulvinar of the optic thalamus; further, these structures themselves 

 and later on the origin of the optic tract of the same side. 



The lower in the animal kingdom one descends the less is the significance of 

 the cortical center, and of the external geniculate body and the pulvinar, 

 which together subserve the function of psychic vision in the higher vertebrates, 

 with respect to the act of vision, while at the same time the anterior quadrigeminate 

 body increases in size, until, finally, in fishes it constitutes the sole visual center. 



In the new-born the optic radiation to the cortex is yet wanting, developing 

 only in the course of weeks. The infant is also up to this time without psychic 

 utilization of what is seen, that is it is for the time being still mind-blind. The 

 deeper centers alone are at first active and excite only reflex action. With the 

 development of the cortical center, the activity of the deeper centers later on 

 diminishes to such a degree that, as soon as consciousness has developed, blind- 

 ness occurs after destruction of the psycho-optic centers. In certain varieties of 

 hysterical impairment of vision it appears that while the cortical center is still 

 functionally active the mind of the patient does not appreciate what is seen. 



The psycho-auditory center or auditory sphere is situated on each side 

 (crossed) in the temporal convolutions, particularly in the root and the 

 posterior portion of the first and concealed in the wall of the fossa of 

 Sylvius. Total destruction of this center causes deafness; partial injury 

 on the left side may give rise to mind-deafness. Among the phenomena 

 of the latter is verbal deafness, which has been observed alone and also 

 in association with verbal blindness. Wernicke found in cases of word- 

 deafness softening in the posterior third of the first temporal convolution 

 (T 1 ) on the left (!), and Naunyn designated the third and fourth fifths 



