Sfainirig Procedures 



115 



decolorizino, and other solutions can result in a poorly stained slide. 

 Hematoxylin-eosin staining (page 130) provides a simple example. If 

 the eosin (counterstain) is applied before the hematoxylin (nuclear) 

 stain, the former stain will be completely removed during the action of 

 the latter stain. 



If slides are to be transported in quantity, rather than individually, 

 several types of holders are useful and are on the market. A.H. Thomas 

 has one holding 50 slides; Wards has one for six slides. Some are baskets, 

 others are clips, and fit into special staining dishes. The tissue-processing 

 machines are equipped with slide carriers to fit the instrument. Phos- 

 phor-bronze spring wire, 0.05 inch di- 

 ameter, can be fashioned into coils of 

 I inch diameter and cut into any length 

 to hold any^vhere from 3 or 4 slides up 

 to 15 or 20. (Fig. 23) This combination 

 of slides and coil can be used in rectangu- 

 lar staining dishes with the slides resting 

 on their long edges, or standing upright 

 in tall stender dishes. 



A final processing of slides is necessary 

 to make permanent preparations for ex- 

 amination and storage without deteriora- 

 tion. All alcohol and water must be 

 extracted (with certain exceptions) and 

 a medium applied which maintains the 

 tissues in a clear and transparent condi- 

 tion, does not alter the color or intensity 

 of the stains, and holds a cover glass in 

 place. The water is removed through increasing concentration of alco- 

 hol until absolute alcohol is reached. The final reagent is xylene (or 

 the like) to remove the alcohol and make the sections lose their opacity 

 and thereby become clear. Finally a mounting medium (mountant) 

 is applied and the cover glass lowered into place completely covering 

 the sections. (The solvent of the mounting medium usually is either 

 toluene or xylene.) 



Figure 23. A staining coil 

 carrying multiple slides. 



Mounting a Cover Glass 



The tidiest method for mounting a cover glass is this: (1) apply a thin 

 streak of medium on the cover glass (Fig. 24); (2) turn cover glass over 

 and rest on edge (shortest side of rectangles) on the slide, to left of 



