Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 55() PHYSIOLOGY flat, so that the eye is accominodated for intinite distanee, Wlieii tlie eye is to be accommodated for near objects the ciliary processes are pulled forwards and inwards by the contraction of the ciliary muscle, and so tlie suspensory ligament is relaxed and the front of the lens allowed to bulge forwards. The ciliary muscle rmis from the corneo-sclerotic junction, to be attached to the ciliary processes and front part of the choroid. Accommodation is a voluntary action, althoug
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 55() PHYSIOLOGY flat, so that the eye is accominodated for intinite distanee, Wlieii tlie eye is to be accommodated for near objects the ciliary processes are pulled forwards and inwards by the contraction of the ciliary muscle, and so tlie suspensory ligament is relaxed and the front of the lens allowed to bulge forwards. The ciliary muscle rmis from the corneo-sclerotic junction, to be attached to the ciliary processes and front part of the choroid. Accommodation is a voluntary action, although the ciliary muscle consists of unstriated fibres. Contraction is brought about through the intervention of the short ciliary nerves, which are derived from the third nerve. The nucleus of Fig. 248. Diagram showing change in lens during accommodation. M. Ciliary muscle. I. Iris. L. Lens. V. Vitreous humour. A. Aqueous humour. C. Cornea. the third nerve is situated in the extreme hinder part of the third ventricle and the anterior part of the iter of Sylvius. The centre presiding over the movement of accommodation occupies the most anterior part of this nucleus. Movements of the Iris Accommodation for near objects is always associated with contraction of the iris, the function of which we must now consider. In an ordinary spherical biconvex lens the rays of light passing through the periphery of the lens come to a focus at a nearer point than the rays passing through the central parts. In this way a certain amount of blurring of an image is produced, which is spoken of as spherical aberration. This spherical aberration may be corrected in three possible ways:
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