PRACTICAL NOTES ON HISTOLOGY. 225 



the sunlight. Change the fluid after two days, and add one 

 drachm of methylated spirit or alcohol to prevent mildew. Place 

 after another two days in distilled water, and scrape off the 

 epithelium. Change the water to get rid of debris ; next separate 

 the cornea into two, three, or more lamellae. Float on a slip, add 

 cover-glass, and run in glycerine. The rabbit's cornea may be 

 prepared as above for nerve preparations. 



Isolation of Corneal Corpuscles.— Stain corneal corpuscles 

 with gold ; then dissolve away the intermediate substance by 

 caustic alkali, the action of which must be arrested before the 

 corpuscles and nerves are destroyed. This is done by divesting it 

 of epithelium in a watch-glass containing a strong (20 per cent.) 

 solution of caustic potash or soda, and this is then put into a warm 

 chamber at 40 deg. C, 104 deg. F. After three-quarters of an 

 hour the tissue, which is now quite soft and pulpy, is removed 

 with a section-lifter, and placed in a vessel containing a large 

 quantity of water faintly acidulated with acetic acid. Then mount 

 in glycerine. 



Cell-Spaces of the Cornea.— These are shown by two methods : 

 — {a) The cornea, after the epithelium has been scraped off the 

 front, is rubbed with a stick of fused nitrate of silver (lunar 

 caustic). After five minutes wash the surface with a stream of 

 distilled water from a wash-bottle. The head is now cut off and 

 placed in spirit in the light for a time varying from a few minutes to an 

 hour. When it is brown, remove and leave in a dark place for 

 twenty-four hours. Slice off the cornea, place in water, slit in a 

 triradiate manner, so that it may lie flat on the slide, and mount 

 in glycerine. 



{b) To inject the cell-spaces, take the eye of any animal, make a 

 solution of alkanet in turpentine, and fill the tube and fine steel 

 canula ; insert obliquely into the substance of the cornea, but 

 avoid passing the point into the anterior chamber. The pressure 

 of the mercurial apparatus is gradually raised to about two inches 

 of Hg. (mercury), Avhen the red fluid gradually fills the cell-spaces. 



To examine the Nuclei of the Cornea —Place the entire eye 

 of a rat in half per cent, gold solution for half-an-hour, then for 

 several days in weakly acidulated water, excise^ and stain it in 



