xix THE EYE AND THE SENSE OF SIGHT 213 



pressure, it recovers its original curvature and shape when 

 the pressure is removed. We have seen that the lens is 

 kept in its place by the suspensory ligament passing off from its 

 edge to the ciliary processes all round it. The lens itself is 

 enclosed by a transparent membrane, thicker in front than 

 behind, called the capsule of the lens. It is to this capsule 

 that the suspensory ligament is attached, but the suspensory 

 ligament not only joins the capsule at the edge of the lens, 

 but becomes directly continuous with the part of the capsule 

 covering the front of the lens. This ligament is naturally 

 tight, so that it is always more or less compressing the front 

 of the lens, making this surface less convex than it would 

 otherwise be. When we are looking at distant objects the 

 pressure of the suspensory ligament is reducing the curvature 

 of the front surface of the lens as much as possible, so as to 

 make the lens weak. In this condition also is the lens when 

 the eye is at rest, as during sleep. From the junction of the 

 cornea and sclerotic there are fine unstriated muscle fibres 

 passing downwards into the ciliary processes. These form 

 a continuous ring of delicate muscle, called the ciliary 

 muscle. When this muscle contracts, the ciliary processes 

 with the loosely-attached choroid are drawn upwards towards 

 the origin of the muscle from the junction of the firm and im- 

 movable sclerotic and cornea. As the ciliary processes are 

 moved they carry with them the attachment of the suspensory 

 ligament up nearer to the lens ; thus the whole suspensory 

 ligament is slackened. When we look at a near object this 

 muscle contracts, and so slackens the suspensory ligament, and 

 the lens, the pressure on its anterior surface being lessened, 

 lii-i 'nines by its own elasticity more convex. 



Short Sight and Long Sight. Ordinary persons cannot 

 see things clearly when these are nearer than 5 or 6 inches to 

 the eye, because the lens cannot be made convex enough to 

 bring the rays to a focus. A short-sighted person sees things 

 very well, and, in fact, best when they are as close as, or even 

 much closer than this. But a short-sighted person cannot 

 see things distinctly when they are some little distance off. 

 because, however much his lens is flattened by the suspensory 

 ligament, it brings the rays from a distant object to a focus in 

 front of the retina. To correct this concave spectacles have 



