The commoner diseases of the eye : how to detect and how to treat them . reatment.—Nystagmus andits causes. The center about which the eyeball rotates issituated in the line of its visual axis, about 14mm. behind the cornea. Six muscles turn (notdraw) it in every possible direction, as well asgive it a sort of zvheel motion on its axis. Ifit were possible for them to operate separatelywe might regard the external rectus as rotatingthe globe directly outwards, the internal rectusas turning it directly inwards, the superior rectusas rotating it directly upwards, the inferior rectusas turning it
The commoner diseases of the eye : how to detect and how to treat them . reatment.—Nystagmus andits causes. The center about which the eyeball rotates issituated in the line of its visual axis, about 14mm. behind the cornea. Six muscles turn (notdraw) it in every possible direction, as well asgive it a sort of zvheel motion on its axis. Ifit were possible for them to operate separatelywe might regard the external rectus as rotatingthe globe directly outwards, the internal rectusas turning it directly inwards, the superior rectusas rotating it directly upwards, the inferior rectusas turning it directly downwards, while morecomplicated movements in various directions areeffected by the combined action of these with thesuperior and inferior oblique muscles. 426 COMMONER DISEASES OF THE EYE As a matter of fact, no movement of eitherglobe—to say nothing of their combined move-ments—is effected by less than two or threemuscles; probably every rotation is attended bythe contraction or relaxation of all of fourth nerve supplies the superior oblique,. External Muscles of the Eye. (Nimier and Despagnet.)the external rectus is supplied by the sixth nerve,while the other ocular muscles (including thelevator palpebra superioris, the sphincter pupil-lae and the ciliary muscles i are innervated by theoculomotorius—the third cerebral nerve. *A useful aid in remembering these innervations isthe radical SO» (superior oblique, fourth nerve).Memorizing this fact, all one has to bear in mind isthe sixth nerve supply to the external rectus and thethird nerve to all the other muscles. COMMONER DISEASES OF THE EYE MUSCLES 427
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