244 Specific Examples of Slide Making 



the stain to hold it in the nuclei, and, if the slide is placed in acid-70 per 

 cent alcohol, it will be found that the stain diffuses out from the nuclei 

 which, instead of appearing clear and sharp, appear, as it were, blurred 

 around the edges as in an out-of -focus photograph. Differentiation by roll- 

 ing back the stain with 96 per cent alcohol gives a clear sharp stain, which 

 is as well differentiated as any of the iron alum mordant stains, but which 

 has the advantages of giving a greater transparency and also of staining 

 the background sufficiently to render it apparent for class demonstration 

 purposes. 



The slides may remain in the saturated solution of lithium chloride in 70 

 per cent alcohol for as long as is required, being subsequently passed 

 directly through the higher alcohols to xylene and mounted in balsam or 

 some synthetic substitute for it. 



This technique may, of course, be applied to accumulating and staining 

 selected sections from any series cut from any material. 



SUMMARY 



1. Remove a 72-hr chick embryo from the egg and fix it as described in 

 Example 3. 



2. Wash, dehydrate, clear, remove from paper support, embed in wax, 

 and cut a complete series of 10-/J. sections throughout the whole embryo. 



3. Remove from the ribbon those portions from which sections are to be 

 mounted. 



4. Flood a clean slide with diluted Mayer's albumen. Place selected sec- 

 tions in order, but without regard to symmetry, on fluid. 



5. Using two brushes, bring the two end sections into position. Fuse the 

 edges together in two places with a hot needle. Join the other sections 

 in order until a ribbon has been formed. Warm to flatten sections; drain 

 and dry. 



6. Dewax dried sections and pass to 90% alcohol through usual re- 

 agents. 



7. Stain until nuclei darken (1 to 3 min) in Ehrlich's acid alum hema- 

 toxylin. 



8. Take each slide individually and flush surface with 96% alcohol 

 from a pipette. When sufficient stain has been removed, place slide in a 

 saturated solution of lithium carbonate in 70% alcohol until blue. 



9. Dehydrate, clear, and mount in balsam. 



