. A text-book of physiology : for medical students and physicians . in theequatorial plane of the eye, and rotations around any of them movethe eyeball obliquely upward or downward. These definitions allhave reference to what is known as the primary position of the 368 BINOCULAR VISION. 369 eves—that is, that position taken by the eyes when we look straightbefore us toward the horizon,—a position, therefore, in which theplane of the horizontal axes is parallel to the ground; all otherpositions of the eyes are spoken of as secondary. With regard to the movements of the eyes about its axes ofrot
. A text-book of physiology : for medical students and physicians . in theequatorial plane of the eye, and rotations around any of them movethe eyeball obliquely upward or downward. These definitions allhave reference to what is known as the primary position of the 368 BINOCULAR VISION. 369 eves—that is, that position taken by the eyes when we look straightbefore us toward the horizon,—a position, therefore, in which theplane of the horizontal axes is parallel to the ground; all otherpositions of the eyes are spoken of as secondary. With regard to the movements of the eyes about its axes ofrotation the following general statements are made: Starting fromthe primary position, rotations of the eyes about the vertical axis—that is, movements directly to right or left—may be made by thecontraction of the internal or the external rectus as the case may around the transverse axis—that is, movements directlyup or down—require in each case the co-operation of two movements upward the superior rectus, acting alone, would in. Fig. 157.—Diagram showing for the left eye the paths of the line of sight caused by theaction of the different eye-muscles (Hering). The horizontal line indicates movements out orin to various degrees as caused by the contraction of the internal or external rectus. Thecurved lines show the amount of torsion given the eyeball by the superior and inferiorrectus and the superior and inferior oblique when contracting separately. Tne shortheavier line at the end of the paths indicates the position of the horizontal meridian atthe end of the movement. R. e., the external rectus; R, i., the internal rectus; R. S.,the superior rectus; R. inf., the inferior rectus; O. i., the inferior oblique; 0. S., the superioroblique. rotating the eyeball upward also give it a slight torsion so as toturn the upper part of the vertical meridian inward. To obtain amovement directly upward (rotation around the transverse axis)the superior rec
Size: 1681px × 1486px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, booksubjectmedicine, booksubjectphysiology
