56 Animal Microloyy 



3. Xylol Used for Removing Paraffin should be kept in a jar separate from 

 that which contains xylol for clearing before mounting and it should be 

 changed occasionally because it tends to become saturated with paraffin. 



4. Sections Not over 10 Microns Thick may be plunged directly from 95 

 per cent, alcohol into an aqueous medium and vice versa. If sections 

 are over 10 microns thick it is better to put them through the complete 

 series of alcohols. With thick sections diffusion is less rapid, and too 

 abrupt a change from one fluid to another may produce distortions or 

 wrench the sections loose from the slide. 



5. To Avoid Rubbing Sections off the Slide, hold the slide with one end 

 toward the light before wiping it and glance obliquely along the surface. 

 The shiny side is the one to wipe. 



6. The Series of Alcohols and Stains ordinarily may be used a number 

 of times without replenishing. When the alcohols become very much 

 discolored or the stains cloudy they should be renewed. Alcohols should 

 not be used too often, however, as they soon accumulate particles of dirt 

 which settle upon the sections and render preparations unsightly. 



7. Absolute Alcohol must be kept free from water. It may be tested 

 from time to time by mixing a few drops with a little turpentine. If the 

 mixture appears milky the alcohol contains a harmful amount of water 

 and should be renewed. 



8. Two Slides Placed Back to Back can be handled as readily as a single 

 slide in passing through the various liquids. 



9. Gentle Agitation of a Slide in any liquid facilitates the action of the 

 liquid. Observe this precaution especially with absolute alcohol. 



10. For Washing Sections after Staining in Hematoxylin tap water is 

 preferable to distilled water because it is usually slightly alkaline. 

 When acid alcohol is used to decolorize sections stained in hematoxylin, 

 the sections should be washed in 70 per cent, alcohol rendered alkaline 

 by the addition of a few drops of 0.1 per cent, solution of bicarbonate of 

 soda. The alkali neutralizes the acid and restores the bluish-purple 

 color to the section; it also renders the blue color more permanent. If 

 too much of the soda is added the color will be a hazy disagreeable blue. 



11. To Obtain a More Precise Stain with Delafield's hematoxylin it is 

 well to dilute it with three or four times its bulk of distilled water. 

 The sections must be left in this solution a correspondingly longer time. 

 Sections stained in this way may not require treatment with acid alcohol. 

 Most workers, however, prefer to overstain and decolorize. 



12. The Length of Time Required for Staining Different Tissues is exceed- 

 ingly variable. Upon removal from the stain after rinsing, if the sections 

 are insufficiently colored, put them back into the stain and examine from 

 time to time until they are properly stained (30 minutes to 24 hours). 



13. If Objects Refuse to Stain it is usually due to one of the follow- 

 ing causes : (a) The fixing agent has not been sufficiently washed out. 



