52 Animal Micrology 



alcohol (a few seconds) when the sections are in 70 per cent, 

 alcohol. 



4. Stain for 10 to 20 seconds in Lyons blue. It is very easy 

 to overstain with this dye. 



5. Rinse in 95 per cent, alcohol, and transfer the sections to 

 absolute alcohol (3 minutes), clear in carbol-xylol, and mount in 

 balsam. 



IV. STAINING WITH HEIDENHAIN'S IRON-ALUM HEMATOXYLIN 



This stain is very valuable in the study of cell division and in 

 determining the finer structure of the nucleus. The iron-alum 

 acts as a mordant, preparing the tissue for the action of the 

 hematoxylin. 



1. Prepare two sets of sections of intestine, testis or ovary, 

 bladder, pancreas, and stomach. The sections should not be over 

 6 or 7 microns in thickness. Preserve one set for double 

 staining. 



2. Pass the slides bearing the sections through xylol, absolute 

 alcohol, 95 per cent, alcohol, and thence directly into water. 



3. Transfer from water to the iron-alum, and allow this solu- 

 tion to act for from 6 to 8 hours. 



4. Rinse in water 5 minutes. 



5. Stain in the 0.5 per cent, hematoxylin 24 to 36 hours. If 

 a trace of the iron-alum remains in the sections the hematoxylin 

 will turn black. This, however, does not impair its power of 

 staining. 



6. Rinse in water 5 minutes. 



7. Place the sections into iron-alum again, which will now 

 extract the excess of stain. The time required for proper differ- 

 entiation varies with the kind of tissue and the fixing agent that 

 has been used. From 10 to 30 minutes is usually sufficient, 

 though no definite time limit can be set. Remove the slide from 

 the iron-alum from time to time and inspect it. When the sec- 

 tions become of a dull-grayish hue the decolorization is usually 

 sufficient. If very accurate results are necessary, the slide should 

 be removed from the iron-alum frequently and examined under 



