oCO DISEASES OF THE EYES. 



A cataract is usually developed as follows : — " A grey or 

 white speck is seen, after the subsidence of the acute inflamma- 

 tory stage of periodic ophthalmia, in the centre of the pupil ; this 

 grows at each successive attack until it quite fills up the aper- 

 ture ; vision grows less and less distinct during its formation. 

 The growth of the incipient speck during the time that the organ 

 is suffering from ophthalmia is commoidy rapid ; but as soon as the 

 inflammatory action has subsided, its progress becomes compara- 

 tively slow, and now and then it appears to remain quite sta- 

 tionary ; for as soon as cataract has formed, the inflammation 

 generally begins to dechne, and the eye seldom receives another 

 attack ; there are, however, some exceptions to this. And it is 

 also, I beheve, an established fact, that not only does the in- 

 flammation permanently leave the cataractous eye, but, should 

 the other have remained free from the disease, it is in less 

 danger of beins^ attacked. Under such circumstances, there- 

 fore, a cataract is hailed as a favourable omen ; this is expU- 

 cable, seemingly, on the principle of sympathy, which is known 

 to have great influence in ophthalmic pathology, and the cir- 

 cumstance has been considered weighty enough to recommend 

 the artificial destruction of one eye in disease to preserve the 

 other in health." — (Percivall.) 



Although cataract is generally a sequel to periodic ophthalmia, 

 it by no means follows that this is the only cause. Many in- 

 stances of fully developed cataracts in both eyes have come 

 under my immediate observation without any preceding inflam- 

 mation. At the present time I have a carriage-horse under 

 my care. Four years ago I examined liim as to his soundness, 

 and passed him. I have seen him continually during tliis 

 period, and am positive he has not suflered from any acute 

 disease of the eyes. Some two months ago he began to exhibit 

 symptoms of defective vision, by shying, &c. Upon examination, 

 I found a star-like cataract in each eye; these have rapidly 

 increased in size, and they now embrace nearly the whole 

 structure of the lens, but there is not a trace of inflammation 

 in either eye, nor has there been any since I first examined him. 



Writers upon human ophthalmic surgery ascribe cataract to 

 a great variety of causes. 



1st. In some cases a blow in the eye, without any penetration 

 of its tunics, ruptures the capsule; while in others, cataract, 



