232 PRACTICAL NOTES ON HISTOLOGY. 



the retina must be stained in bulk before it is embedded (at least 

 the nuclear stain). The best stains are logwood and carmine ; 

 aniline is not so good. Kleinenberg's logwood and the alcoholic 

 borax carmine have been given. If thick sections are required 

 (as in search of blood-vessels) carmine is preferable, as it is more 

 transparent ; whilst in thin sections Gibbes' or Kleinenberg's 

 logwood is the best. Leave the retinas in carmine about two days 

 and in logwood from twelve to twenty-four hours. The exact time 

 differs according to which hardening agent is used. To show the 

 Miillerian fibres or blood-vessels, the sections of retina which 

 have been stained in bulk with a nuclear stain should be stained 

 (best on the slide) with either fuchsin or an alcoholic solution of 

 eosin, preferably the latter. 



Mode of Preparing and Mounting Sections.— 



I. — Infiltration and embedding in celloidin and freezing. 



2. — ,, „ „ „ celloidin and cutting 



under spirit. 



3.— „ „ „ „ paraflSn. 



4. — ,, ,, ,, ,, cacao butter. 



I and 2. — It is difficult to obtain thin sections by the second 

 method, but fair ones are got by the first. The whole sclerotic, 

 choroid, and retina should be embedded together, and when the 

 celloidin is firm the retina and part of the choroid should be 

 separated with a sharp scalpel. Earlier attempts only result in 

 damage to the rod-layer. 



Staining. — (a) To the water in which the sections have been 

 placed on removal from the microtome add a little eosin. In a 

 few minutes they will be sufficiently stained. (<^) They may be 

 placed at once on the slide with a section-lifter and stained there. 

 Gently wash in either case after staining, and with care nearly dry 

 with filter or blotting-paper. It must then be covered with a few 

 drops of alcohol. On removing this re-agent with blotting-paper 

 {care must be used not to get any fibres on the sections), clear in 

 clove-oil or bergamot and mount in balsam. 



3. — By paraffin method serial sections may be prepared. 



4. — Infiltration and embedding in cacao butter. Stain a part 

 of the eye with a nuclear stain, place it afterwards first in alcohol. 



