ANIMAL MECHANISM. 113 



how the eye is to answer its original design with the 

 loss of one of its important glasses ? 



To couch, an operation often mentioned, and often per- 

 formed, is to thrust a delicate needle through the white 

 of the eye, just on its border, till the point reaches the 

 lens, which is then depressed into the lower part of the 

 eye, below the optic axis, so that light may, by entering 

 the pupil, arrive at the nerve. In this last operation, fears 

 are always entertained, that the lens may rise again to its 

 former position, rendering a repetition of the operation 

 indispensable. Secondary cataracts sometimes form, after 

 couching or extraction, and arise in consequence of a thick- 

 ening and opacity of the capsule, which is left behind. 

 Such cases are more alarming in their progress than a 

 disease of the lens, as no surgeon is warranted in promis- 

 ing even a partial relief. If he attempted to tear away 

 the membrane, he might also rend every other within the 

 globe. 



A few facts of this kind which have a. practical bearing, 

 more or less interesting to every person, may lead to cor- 

 rect views, in relation to some of the diseases which are 

 common to this curious, wonder-working organ. 



FIG. G. 

 Explanation of Figure 6. 



This is a scheme showing how 

 a bad operator, by introducing 

 the couching needle too near the 

 cornea, may rupture the ciliary 

 processes, and actually divide 

 the lens in two pieces, without 

 moving it from the optic axis. 

 A The vitreous humor, 

 B The lens. 

 CC Ciliary processes, torn by 



the lower part of the need's, 



thereby doing great violence 



and a permanent injury to the 



organ. 



DD The iris. 

 E The anterior chamber of the aqueous humor. 



VOL. I. NO. V. 



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