Cataract. Opacity of the Lens or Its Capsjile. 429 



inflammation of the iris, choroid, ciliary body, retina, or hyaloid 

 membrane, and above all, in solipeds, in recurrent ophthalmia. 

 It may be assumed that a transparent tissue composed of cells 

 can only maintain its translucency so long as the most perfect 

 equilibrium is maintained as regards the mutual relation of the 

 cells, the pressure of its interstitial plasma, and the chemical 

 composition of both plasma and cell structures. The slightest 

 deviation in any direction will impair or abolish the transparency 

 of the tissue. In inflanunation this occurs in various ways, 

 through the increased cell multiplication and the change in the 

 nature of the cells, through the increased exudation and the alter- 

 ation of the solid parts as regards compression and relative posi- 

 tion, and through chemical changes in the exudate which contains 

 more salts, fibrinogenous material, etc., than the normal plasma. 

 The same is true of all the post inflammatory degenerative pro- 

 cesses that take place in the lens. 



The formation of cataract from chemical alteration in the 

 fluids is familiar in diabetic subjects, — man or beast (Altenhof). 

 It can be produced experimentally in frogs by injecting sugar, 

 common salt or anj' other readily diffusible saline solution under 

 the skin (Kunde). Rabbits that are fed naphthalin develop 

 cataract which radiates in lines and .streaks from the pole towards 

 the periphery and in the cortical portion of the lens. Perhaps 

 the lamellar cataract of rachitic patients is also to be attributed 

 to the lack of earthy salts in the plasma of the lens. 



Senile cataract may be hypothetically attributed to impaired 

 nutrition, degeneration in the lens or its capsule, or less common- 

 ly to disease of the blood vessels of the eye, or gradual changes 

 in the plasma. It occurs in hor.se, ox or dog at ten years old and 

 upward. 



Anterior Capsular Cataract sometimes results from the 

 deposition of blood pigment on the capsule in cases of extra- 

 va.sation into the anterior chamber. This is closely allied to the 

 black or spurious cataract which consists in the adhesion of the 

 uveal pigment to the capsule, and its detachment from the iris. 



Kunde who caused cataract in frogs b)- injection, subcutem or 

 ingestion of concentrated solutions of sugar or .salt, attributes the 

 result to the sudden abstraction of water from the cry.stalline 

 lens. Even the cell multiplication in inflammatory cases, he 



