THE VITREOUS HUMOR. 271 



weeks, vertical sections may be made, one of which 

 should pass through the centre from before back, and 

 should be as complete as possible. They are to be 

 mounted in glycerine. The lens must not be put in 

 spirit, or at all events not in strong spirit, to com- 

 plete the hardening, for this renders the tissue, 

 especially the central parts, quite hard and horny, 

 and the outlines of the fibres become obliterated. 



Preparation 36. The epithelium of the lens- 

 capsule, This may have been seen in the antero- 

 posterior section as a. single row of nucleated cells, 

 lying immediately behind the anterior part of the 

 capsule. To show it on the flat it is to be stained 

 with nitrate of silver. With this object a lens still 

 inclosed in its capsule is removed from a fresh eye, 

 and, after having been rinsed in distilled water, 

 transferred for five minutes to J per cent, nitrate of 

 silver solution. It is then again washed with dis- 

 tilled water, and placed in the light in weak spirit 

 (equal parts spirit and water). When brown it is 

 removed from the light, and after twenty-four hours 

 the substance is hard enough to allow tangential 

 sections to be made from the anterior surface, which 

 shall include the capsule, the epithelium and the 

 parts of the lens substance immediately subjacent to 

 this. The sections are mounted in glycerine with the 

 brown surface uppermost: and through the elastic 

 capsule, which is not distinctively stained, the out- 

 lines of the epithelium-cells are clearly seen. At 

 places the silver solution may have penetrated to the 

 superficial lens fibres, and will be found to have 

 stained the cementing substance between them. 



Preparation 37. The zonule of Zinn and the. 

 hyaloid membrane of the vitreous humor. 

 Take the anterior half of the eye (preserved in spirit) 

 of an albino rabbit, and having pinned the cornea 

 downwards on a loaded cork under spirit, and re- 

 moved the remains of the vitreous humor, gently 

 seize the lens with fine forceps, and draw it away 

 from the iris. In doing this it will drag with it tie 



