THE WINDOWS. 151 



eye a window, the comparison is a very happy 

 one. 



The edges of the iris or curtain, however, 

 like a partition, divide this glassy liquor into 

 two masses, connected only at the pupil. The 

 part of it which is before the iris is called the 

 aqueous humor, and that which is behind it, 

 and which is many times the largest, the vitre- 

 ous humor. 



Just behind the iris, or rather exactly behind 

 the pupil, is a small body, clear and transpa- 

 rent, like the rest of the vitreous humor, but 

 much harder, and swimming, as it were, in its 

 midst, without ever getting out of its place. 

 It is called the crystalline lens. It is rounded 

 or convex on both sides, and resembles two 

 watch crystals, with their hollow or concave 

 sides put together. 



It is represented in the engraving, by a light 

 spot, which you cannot fail to distinguish, near 

 the fore part of the eye. There is .a kind of 

 disease of the eye, in which this lens turns 

 whitish ; and as the rays of light can no longer 

 pass through it, the person becomes blind. 

 The only way to cure it is for the surgeon to 

 pass a slender needle through the side of the 



