5o6 



HISTOLOGY 



upon it. It is perhaps best to make a practice of using the egg fixative in all 

 cases. 



The slides can now be stored for some time in dust-proof boxes. It is best, how- 

 ever, to proceed soon after this to stain and mount them. We shall continue our de- 

 scription of a particular example. 



Rinse in distilled water and transfer to a one fourth of i per cent solution of haema- 

 toxylin in distilled water. Experience will tell how long to stain. From six to twelve 

 hours is usually right. The longer stain will bring out the achromatic and cytoplasmic 

 structures best. 



When stained, the slides must be rinsed and returned to a somewhat weaker solu- 

 tion of the same iron alum that was used to mordaunt them. They must be watched 

 while the color is extracted and had best be frequently taken out, rinsed, and examined 

 with an old microscope to see that the proper reaction has taken place. They will 

 look darker when finally mounted than when thus examined in water. The stained 

 slides should now be washed in gently running tap-water or in a number of changes of 

 fresh water to remove all traces of the iron alum. They are then ready for 



MOUNTING 



Drain off excess of xylol and promptly place a drop of some good, acid-free balsam 

 solution on the specimen, which should still be wet with xylol. It must at no time be 

 allowed to dry. Use Griibler's damar balsam dissolved in xylol. The cover glass, of 

 number one glass, should now be placed in position without pressing on its top when in 

 place, and the slide laid flat in a warm place. Any air bubbles which happen to be 

 inclosed will find their own way out in a few days, if the proper amount of balsam is 

 present. Balsam may be added in small drops at the edge of the cover. The balsam 

 should be diluted, if too thick, with pure, fresh xylol. 



The above is a single concrete example. We shall suggest as a desirable variation 

 the following 



SECOND EXAMPLE 

 A A. Fix bits of the same tissue in Flemming's solution of 



1 per cent chromic acid ........ 15 parts 



2 per cent osmic acid ......... 4 parts 



Glacial acetic acid . ....... i part 



