222 PRACTICAL NOTES ON HISTOLOGY. 



mosaic of the cut fibres is visible. Hydrochloric acid (o*i to 

 I per cent.) may also be used. The capsule can be seen in 

 fresh, but better in preparations stained with purpurine or aniline ; 

 and cells on the posterior surface of the anterior segment of the 

 capsule by gold preparations or the aniline stains. Silver nitrate, 

 one-half per cent., will also bring them out well. To best show 

 the surfaces of the lens fibres covered by narrow, elongated cells, 

 take the lens of a toad, which is removed fresh, and placed at 

 once in one-half per cent, of gold solution, in which break it into 

 fragments with needles. Let them remain for thirty minutes, 

 exposed to sunlight, in 2 per cent, acetic acid for several days or 

 until they acquire a dark colour. Examine in glycerine. If the 

 eyeball is injected through the aorta with a quarter per cent, solution 

 of gold, kept tense for some minutes, the cells may be fixed (71 

 situ. Then stain some fragments of the lens in a concentrated 

 solution of logwood and examine in glycerine. Similar prepara- 

 tions can be obtained by injecting the aorta or carotid of the rat 

 or rabbit. 



Zonule of Zinn and the Hyaloid Membrane of the Vitreous 

 Humour.— Take the anterior half of the eye (preserved in spirit) 

 of an albino rabbit, pin the cornea downwards, remove under 

 spirit the remains of the vitreous humour, gently seize the lens 

 with fine forceps, and draw it away from the iris. In so doing, 

 you draw with it the suspensory ligament, the zonule of Zinn, and 

 the part of the hyaloid membrane continuous with this, so that 

 the separated lens appears girdled by a delicate, somewhat 

 crumpled-looking, membranous zone. Cut out with scissors a 

 segment of the zone, and with a section-lifter transfer the piece so 

 removed (it should include its whole breadth) to logwood. Wash 

 in water, float on a slip, and replace the water by glycerine, or 

 instead mount as usual in Canada balsam. 



The Retina.— For general use, Miiller's fluid is good; but it 

 causes the retina to become brittle. It, however, shows the nervous 

 structure best. Chromic-acid mixture renders it more tough and 

 shows the connective tissue. Good sections are obtained by 

 DOUBLE-STAINING the whole eye of the frog. Place, first, in a 

 strong solution of rosanilin until it is deeply stained, and wash 



