Eyes and other Objects. 65 



diately surrounding this is the black lining of the eye, 

 and the remarkable structure suspended in the 

 vitreous humour, not in its centre, but near its front, 

 is the crystalline lens spherical in fish, but of the 

 form called double-convex in man and in various 

 lower animals. The shaded appendage at the right 

 of the eye is the optic nerve, which expands inside the 

 eye-ball into a delicate cup-shaped membrane called 

 the retina, exactly answering to the slightly concave 

 round table inside a landscape camera. 



I have seen all this mechanism shown with a cow's 

 eye, cleverly arranged by a physician, who exhibited it 

 to a large party. The front view of the iris in a 

 detached eye is not a very agreeable sight; but I 

 believe most of the lookers-on forgot its unpleasant- 

 ness when the section of the eye was made, and the 

 crystalline lens displayed in its brilliant polish and 

 transparency 



The lenses in our own eyes (according to an in- 

 teresting article in the "Penny Cyclopaedia") are 

 " composed of an infinite succession of thin concen- 

 tric laminae, arranged with the utmost regularity one 

 within another, like the coats of an onion, and every 

 such stratum or elliptic shell is made up of a series of 

 exquisitely minute fibres laid side by side." The 

 writer goes on to say that similar though not precisely 

 the same arrangements are observed in the eyes of 

 other animals ; and that in fish these fibres f ' are 

 curiously hooked together by fine teeth." The lens 

 is always enclosed in a delicate skin or capsule this 

 can easily be made out in the boiled eye of a fish ; so 



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