XXX II.] THE EYE. 365 



slum (2436 hours). Tease out a fragment of the softened lens in 

 glycerine. (/>.) Or use dilute sulphuric acid (4-5 drops to 5 cc. of 

 water for 24-36 hours). Wash in water to remove the acid. Stain 

 in carmine or liseinatoxylin. (c.) Methyl-green feebly acid, does well 

 for fresh-teased fibres, but the preparations do not keep. The 

 nuclei on the fibres may be seen in this preparation. 



(H) (a.) Observe the flattened bands with serrated edges; the 

 teeth dove-tail into each other. The teeth may be seen from the 

 side or directed to the observer. 



RETINA. 



Methods. (i.) With a sharp razor cut the eye of a cat, rabbit, 

 pig, or other animal into an anterior and posterior half. Place the 

 posterior half in 2 per cent, potassic bichromate, or in a mixture of 

 Miiller's fluid and spirit (two weeks), and complete the hardening 

 in spirit. 



(ii.) Stain "in bulk" in. borax-carmine for several days the 

 whole posterior segment of the hardened eyeball, then place it for 

 a day in acid alcohol, and embed in paraffin and cut sections. Per- 

 haps celloidin is to be preferred if the sclerotic be thick. Fix the 

 sections on a slide and mount in balsam.* In this way the whole 

 structure of the retina is preserved in its relations to other struc- 

 tures. 



(iii.) The same process may bo adopted with the posterior seg- 

 ment of the eyeball hardened in i per cent, osmic acid. 



(iv.) Harden the retina in a 3 per cent, solution of nitric acid 

 (i 5-20 mins.). Wash out the acid, stain in bulk, and make sections. 

 Stain with eosin and methylene-blue. 



(v.) For small eyes, such as those of a lizard, it is sufficient to 

 expose the whole unopened eyeball to the vapour of osmic acid for 

 several hours, and then to stain the eyeball in bulk in borax-carmine. 

 Embed in paraffin and cut sections of the whole eyeball. Or, expose 

 the eye of a frog or triton to osmic acid vapour (10 mins.). Place 

 in 40 per cent, alcohol (4-6 hours) ; divide eyeball by incision 

 parallel to edge of cornea ; bichromate of ammonia (3 per cent.) for 

 5-10 hours; wash in water; alcohol; borax-carmine; embed and 

 cut in paraffin. 



(vi.) Make sections of an eyeball hardened in Muller's fluid and 

 stain them in eosin-hsematoxylin. The latter stains the granular 

 layers of the retina, while the other parts are rosy in tint. 



(vii.) Methylene-Blue Method. This is done cither by injecting 

 methylene-blue (i in 300 normal saline) into the blood-vessels of an 

 animal just killed, and waiting two or three hours thereafter, or by 

 placing the fresh retina in the same fluid and observing with the 



