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

  • Heath, Christopher, 1835-1905.
Date:
1885
Catalogue details

Licence: Public Domain Mark

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

    625/682 (page 533)
    PAET VIII. DISSECTION OF THE EYE. In order to study the general anatomy of the globe of the eye it will be best to procure hali-a-dozen bullocks' eyes, since the parts are larger than in the human eye, which also it is difficult to procure in a sufficiently recent condition. It must be borne in mind however that the eye of the bullock differs from that of man in the following jDarticulars : the cornea is oval instead of being nearly circular ; the pupil is elongated into a slit instead of being a circular aperture ; the choroid coat presents the peculiar coloured appearance known as the tapetum lucidum, which is absent in man ; and the yellow spot which is present in the human retina is wanting in the eyes of quadrupeds. The following description will be of the human eye, which the student will find no difficulty in following. [All the fat and the remnants of the muscles of the eye are to be removed with scissors, the optic nerve being carefully preserved.] The Human Eyeball (Fig. 270) is nearly globular in shape, but has a portion of a smaller sphere (the cornea) projecting anteriorly, thus making its antero-posterior greater than the transverse diameter. The Sclerotic (Fig. 270, ii) or external tunic is composed of dense white fibrous tissue, and serves to maintain the shape of the eyeball and to protect the internal parts. It is thicker behind than in front, and is pierced posteriorly by the optic nerve, which enters at a distance of about its own breadth to the inner side of the axis of the eyeball. The opening in the sclerotic for the optic nerve is funnel-shaped, and the fibrils of the nerve pass through a fine fibrous tissue, which has been named lamina cribrosa from its numerous aper- tures, one of which in the centre for the arteria centralis retince has been called the p or us opticus. The sclerotic is pierced at various points by the ciliary vessels and nerves. In front, the sclerotic gives insertion to the recti muscles, from which it receives an expansion {tunica alhuginea), and in front of this point the conjunctiva is