SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 301 



801. IN THE CASE OP THE SHORT-SIGHTED, at ordinary 

 distances the light is refracted too much, and reaches a 

 focus before it reaches the retina, as in Fig. 4, PI. 8. 

 But as there is nothing to check the light it passes on, 

 spreading beyond the focus, till it reaches the retina 

 and acts over the visual points from b to c, and the 

 same sensations and appearances will result as in the 

 case of the equally long-sighted. 



802. Remark. Figs. 3 and 4, PL 8, represent in colors the same 

 ideas, only more fully, as the light from three points is represented, and 

 it is seen that they overlap each other on the retina, producing confused 

 sensations of color as well as of direction. To a long or short sighted 

 person a point appears to occupy much space, and objects appear blend- 

 ed, indistinct, and of course not in their true colors. 



803. Experiment. It is found that the light passing through the 

 outer part of a lens is not brought exactly to the same focus as that 

 passing through the centre. 



804. ANOTHER USE OF THE IRIS is to cover the cir- 

 cumference of the lens and also shut out light coming 

 through the circumference of the cornea. 



805. It is also found that some colors are not bent by 

 the same medium quite as much as others, and that by 

 putting together SEVERAL MEDIA, each operating differ- 

 ently on different kinds of light, the evil is nearly cor- 

 rected, and in the eye most effectually. 



806. Remark. As the eye, in one position,'can take in but a very 

 limited range of vision, it is important that it be moveable to a very 

 large extent. 



Parts moving the Eye. 



807. AROUND THE EYE a deep, protective, and other- 

 wise useful socket has been formed : narrow at its inner 

 extremity, it widens outward by being funnel-shaped. 



808. Part of THE SPACE BETWEEN THE EYE AND ITS 

 SOCKET is occupied by muscles, blood-tubes, etc., but it 



801. What condition ? 802. Describe Figs. 3, 4, PI. 8. 804. What is ? 

 805. What is the effect of uniting ? 807. What is ? 80S. What said of ? 



