. The principles and practice of medicine, designed for the use of practitioners and students of medicine. e nasal hemianopia may occur as a mani-festation of tabes and in tumors involving the outer fibres of each tract. (4) Affections of the Tract and Centres. The optic tract crosses the crus (cerebral peduncle) to the hinder partof the optic thalamus and divides into two portions, one of which (thelateral root) goes to the pulvinar of the thalamus, the lateral geniculatebody, and to the anterior quadrigeminal body (superior colliculus). Fromthese parts, in which the lateral root terminates,
. The principles and practice of medicine, designed for the use of practitioners and students of medicine. e nasal hemianopia may occur as a mani-festation of tabes and in tumors involving the outer fibres of each tract. (4) Affections of the Tract and Centres. The optic tract crosses the crus (cerebral peduncle) to the hinder partof the optic thalamus and divides into two portions, one of which (thelateral root) goes to the pulvinar of the thalamus, the lateral geniculatebody, and to the anterior quadrigeminal body (superior colliculus). Fromthese parts, in which the lateral root terminates, fibres pass into the pos-terior part of the internal capsule and enter the occipital lobe, forming thefibres of the optic radiation, which terminate in and about the cuneus, theregion of the visual perceptive centre. The fibres of the meditil division ofthe tract pass to the medial geniculate body and to the posterior quadri-geminal body. The medial root contains the fibres of the commissura in-ferior of V. Gudden, which are believed to have no connection with the DISEASES OF THE CEREBRAL NERVES. 1043. su ^^ Fig. 11.—Diagram of visual paths. (From Vialet, modified.) OP. N., Optic C, Optic chiasm. OP. T., Optic tract. OP. R., Optic radiations. GEN., Genic-ulate body. THO., Optic thalamus. C. QU., Corpora quadrigemina. C. C, Corpuscallosum. V. S., Visual speech centre. A. S., Auditory speech centre. M. S., Motorspeech centre. A lesion at 1 causes blindness of that eye; at 2, bi-temporal hemia-nopia; at 3, nasal hemianopia. Symmetrical lesions at 3 and 3 would cause bi-nasalhemianopia; at 4, hemianopia of both eyes, with hemianopic pupillary inaction; at5 and 6, hemianopia of both eyes, pupillary reflexes normal; at 7, amblyopia, espe-cially of opposite eye; at 8, on left side, word-blindness. 1044 DISEASES OF THE XERVOUS SYSTEM. letinse. It is still held by some physiologists that the cortical visual centreis not confined to the occipital lobe alone^, but embraces the
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