Practical anatomy : a manual of dissections / by Christopher Heath.

  • Christopher Heath
Date:
1902
Catalogue details

Licence: Public Domain Mark

Credit: Practical anatomy : a manual of dissections / by Christopher Heath. Source: Wellcome Collection.

    732/798 (page 664)
    among the vessels, and is washed out when the eye is immersed in water. Surrounding the iris is the annular Ciliary Muscle (Fig. 314, 8), composed of unstriped fibre and having a grey appearance. The muscle lies beneath the ciliary processes and is connected anteriorly with the sclerotic coat, close to its junction with the cornea. It consists of both radiating and circular fibres. The radial fibres arise from the junction of the cornea and sclerotic, and from the marginal fibres of the membrane of Descemet around an annular sinus called the canal of Schlemm (Fig. 316, 5); and spread out to become attached to the outer surface of the cilary processes, as far back as the anterior mit of the choroid at the ora serrata. The circular fibres form a ring around the margin of the lens. It is doubtful whether these are not continuous with the radial fibres (Fig. 317). The mode of action of the ciliary muscle is still uncertain. There is no doubt that it is the chief or sole agent in effecting the accom- modation of the lens to near vision, and it is usually believed that by drawing forward the suspensory ligament, with the posterior part of the cilary processes, it lessens the tension upon the elastic lens substance, and so allows that body to become more conyex. It is however possible that the circular fibres may aid this effect by directly compressing the margin of the lens. Fig. 317.—Section of ciliary muscle (after Jevans). a. Radiating fibres of the ciliary — e. Muscular fibres shown in their con- muscle. nection with the corneo-sclero- b. Circular fibres or muscle of Miiller. tic junction. c. Circular fibres surrounded byradi- ff. Iris. ating fibres. g. Uveal tract. d. Circular fibres by themselves. h. Ligamentum pectinatum.