On the anatomy and physiology of the oblique muscles of the eye, in man and vertebrate animals / by John Struthers.

Date:
[1849]
Catalogue details

Licence: Public Domain Mark

Credit: On the anatomy and physiology of the oblique muscles of the eye, in man and vertebrate animals / by John Struthers. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the .rotatory motions occur will always be at right angles to the moving power—transverse when the upper and lower recti act, ver- tical during the action of the lateral recti, and intermediate in the diagonal movements, which are performed by the conjoint action of two neighbouring recti muscles. Again, in the motion of circum- duction, as in turning the eyes round a room, which is performed by the alternate action of the four straight muscles, the centre, as it ■were, still remains unmoved, one end of the axis being depressed as the other is raised, and so on. In accordance with this we find the straight muscles sweeping over the globe of the eye, to become in- serted considerably anterior to its middle, so as to fit them for pro- ducing these various motions; by all of which, it will be observed, the direction of its axis is changed. But it is held by some, that, in- dependent of any change in the direction of its axis, the eye, under certain circumstances, undergoes a movement quite different in its nature—that of rotation on its antero-posterior axis, or what is usually called the axis of the eye,—and that it is the function of the oblique muscles to produce this movement: which I shall call lateral rota- tion. It appeared to me that light might be thrown on this disputed subject by the evidence which comparative anatomy would no doubt afford; for, although the existence of corresponding muscles has been noticed in passing, by various writers on comparative anatomy, the arrangement of them with reference to their action on the eye does not appear to have been inquired into; and, having made careful dissections of these parts, in a great variety of instances, I am en- abled to furnish, from my notes, the following summary of the ar- rangement of the oblique muscles in the different classes of vertebrate animals,—avoiding notice of the comparative anatomy of the other muscles of the eye, as in no way affecting the present inquiry. In Mammalia, the superior oblique has the same general arrange- ment as in man. The differences may be stated thus:—1, That it is usually fleshy for some distance beyond the pulley, and therefore longer, at the same time that it is relatively larger. 2, It is usually not, as in man, directed backwards to the axis of the eye, but meets it nearly at right angles ; and its course from the pulley to the eye is more horizontal than in man : and 3, That its point of insertion is not so far towards the outer and back part of the eye as in man, but is usually only a little external to the vertical axis, and not more behind than in front of it. The insertion varies slightly in different animals, but in the greater number the insertion of the tendon is chiefly concealed by the upper rectus, the posterior border only ap- pearing beyond it; whereas, in man, the tendon passes some way beyond, and also behind the vertical axis of the eye. The inferior oblique, also arising as in man, is not, as in him, directed backwards to the axis, but either forwards or at right angles to it. . But the most striking difference is in the insertion. This in man is towards the posterior part of the eye, but in quadrupeds it is much farther