Nervous and mental diseases . on can still be ob-served, and have the patient fix both eyes upon your finger in the direc-1 Brit. Med. Jour., Sept. 15, 1894. 108 DISEASES OF THE CRANIAL NERVES. tion toward which conjugate movements failed. If the sound eye becovered, it will overact and be turned farther to the side than is re-quired. This overaction, or secondary deviation, is due to the fact thatthe stimulation necessary to draw the affected eye in the direction of theweak muscle is more than sufficient for the corresponding sound you have covered the weak eye in the same way it wi
Nervous and mental diseases . on can still be ob-served, and have the patient fix both eyes upon your finger in the direc-1 Brit. Med. Jour., Sept. 15, 1894. 108 DISEASES OF THE CRANIAL NERVES. tion toward which conjugate movements failed. If the sound eye becovered, it will overact and be turned farther to the side than is re-quired. This overaction, or secondary deviation, is due to the fact thatthe stimulation necessary to draw the affected eye in the direction of theweak muscle is more than sufficient for the corresponding sound you have covered the weak eye in the same way it will not moveoutward far enough when the finger is fixed by the sound eye, and fora similar reason. The direction of failure in the affected eye, therefore,points to the weakened muscle. In marked squint of this characterthe affected eye often presents a much wider range of motion when thesound eye is covered than when binocular vision is attempted. Appar-ently the volitional attempt is stronger when the muscle is not disturbed.
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