LESSONS IN HORSE JUDGING. 45 



jelly, you would thus get a rough representation 

 of the lens of the eye. Now, m the ' lens ' of the 

 eye, our two watch-glasses are represented by a 

 very delicately thin pliable membrane called the 

 'capsule' of the lens, and so the whole 'lens' 

 being firm, but pliable, can be altered in shape by 

 the ' ciliary muscle, ' (Fig. 6, D 2) which is, as we 

 have seen, attached around its margin, so that 

 when this muscle drags the lens backwards against 

 the stiff ' vitreous humour, ' the foremost half of 

 the capsule of the lens (our foremost watch-glass) 

 is bent like a bow that is having its string pulled 

 in the act of shooting, and the lens is thus altered 

 in its convexity from being shaped like B to 

 being shaped like (7, Fig. 5. 



The lens of the eye is quite clear and trans- 

 parent like glass, when in health; but from acci- 

 dent, disease, or old age, it may become opaque 

 and milky, and then the eye is said to have a 

 'cataract.' 'Cataract' may occur from a horse 

 falling on his head whilst hunting, or in rearing 

 and falling back and knocking the head violently 

 against the ground or by knocking the head vio- 

 lently against the top of a doorway — any violent 

 blow on the head, in fact. It does so by rupturing 

 the capsule of the lens (one of our watch-glasses) 

 and letting in the ' watery humor ' which occu- 

 pies the front chamber of the eye, and which is 

 marked x x x x in our diagram (Fig. 5, D). 

 When the 'watery humor' gets into the sub- 

 stance of the ' lens ' through a rent in the capsule, 

 the 'lens' immediately begins to swell and be- 

 come milky and opaque, and in a day or two the 



