224 PRACTICAL NOTES ON HISTOLOGY. 



a double stain of aniline blue and eosine, where the ganglion-cells 

 are to be seen. Those eyes, fixed in alcohol and preserved in 

 glycerine, keep well, such as kittens or frogs. 



Retina of Triton. — Expose to osmium vapour, divide by an 

 equatorial incision, and put the posterior pole for a few hours into 

 an aqueous mixture of one-third alcohol. Stain for some hours in 

 picro-carmine (i to loo); treat again with osmic acid to fix the 

 elements. Wash in water and harden in alcohol. Imbed in oil 

 and wax, cut sections, and mount in glycerine. 



Cornea.— First cut sections and study those made vertically to 

 its surfaces. Use the anterior part of the eye. Harden in Miiller 

 and chromic acid mixture, or 2 per cent, bichromate of potash. 

 (It is well to remove the lens to allow the fluid to penetrate freely 

 to the posterior surface of the cornea.) Cut and stain, and mount 

 as usual. 



Epithelium, covering the front of the cornea, must be studied 

 in teased preparations, which is done by placing in a drop of 

 distilled water on a slide. Stain in logwood, picro-carmine, or 

 gentian-voilet and mount in glycerine, all to be done on the 

 slide. The glycerine can be easily made to replace the logwood 

 solution, or by Klein's gold method. 



The Substantia propria is seen by teasing out a fresh cornea, 

 or one macerated in a weak solution of bichromate of potash or 

 in picric acid, or it may be seen in gold preparations of the 

 nerves. 



Corpuscles and Nerves in Frog's Cornea.— Destroy the brain 

 and spinal cord, hold the viembraiia iiictitaiis with the forceps, and 

 remove it entirely. The animal is then taken and held in the 

 operator's left hand, press the thumb upwards under the lower 

 jaw, to cause the protrusion of the eye. Insert the scissor- 

 blades into the globe of the eye just behind the insertion of the 

 yellowish iris. Remove the anterior part and place in salt 

 solution in a watch-glass. Pour off the salt solution, leaving just 

 enough for the cornea to float in. Fill up the watch-glass with \ 

 per cent, solution of gold chloride. Leave for half-an-hour, place 

 in acidulated water (acetic acid), and deposit in a warm place in 



