STAINING OF SECTIONS 119 



section floating off during the process of staining in the watery 

 solutions. 



2. Place the section in xylol which will dissolve out the paraffin. 



3. Next, place in alcohol which will wash out the xylol. 



4. Remove the alcohol by placing the section in water. 



FIG. 55 



Small student's microtome for sectioning celloidin or paraffin-embedded tissues. 



Staining of Sections. The section is now ready to be treated by one 

 of the various aniiin-staining solutions used to demonstrate bacteria. 

 It is frequently advantageous to first stain the section by some of 

 the methods used in normal or pathological histology, in order to 

 bring out clearly the cellular elements of the tissue itself. If this 

 is done it is generally best to stain the tissue in bulk before it is 

 embedded. 



Carmin Stains. Most useful for such staining in bulk are the 

 carmin stains, particularly alum carmin, which is prepared as follows: 



Carmin 2 grams 



Alum . . . . ' ; . " ... . . . . 5 grams 



Water . . '. ". .' . ". . . . . ^ .... 100 c.c. 



Boil twenty minutes, then add enough water to make up for the loss 

 in evaporation. When cool, filter and add a crystal of thymol to pre- 

 vent the growth of moulds in the staining solution. Tissues to be 

 stained in bulk should be left in this carmin solution for from two to 

 three days; they are then placed for one to two hours in acid alcohol 



