58 BACTERIOLOGY 



had the lower side ground flat. If a razor is used, a special form 

 of razor-holder must be attached to the microtome to receive the 

 razor. Above all, it is necessary that the knives should be kept 

 in good condition. Only occasionally will they need honing, using 

 a fine water-stone or Belgian hone. The movement in honing 

 should be from heel to toe, always placing the back of the knife 

 next the hone when turning. The knife should be stropped fre- 

 quently. The leather of the strop should be glued to a strip of' 

 wood to make a flat surface. The movement in stropping should 

 be from toe to heel. Sections should be cut to a thickness of not 

 more than 25 /*. Thinner sections (5 to 10 fi) are to be desired. 



Staining of Section. — A watery solution of one of the aniline 

 dyes is used — fuchsin, gentian violet or methylene blue — made 

 by adding a few drops of the alcoholic solution to a dish filled 

 with water. Loffler's solution of methylene blue serves very 

 well. 



By this process most bacteria are stained; also the nuclei of 

 cells; frequently, also certain granules contained within some cells 

 which may easily be mistaken for bacteria by the inexperienced 

 (basophilic granules). 



(a) Place the section in the staining solution from two to five 

 minutes. 



(b) Wash in water. 



Place in a watery Solution of acetic acid, i per cent, for 

 one minute. 



(d) Alcohol, one to two minutes; change to absolute alcohol. 

 Touch the sections to blotting-paper to remove the superfluous 

 alcohol. 



(e) Xylol until clear; xylol is to be preferred to other clearing 

 agents, like oil of cloves, most of which slowly remove aniline 

 colors. It has the disadvantage of not clearing when more than a 

 trace of water is present; dehydration in alcohol must, therefore, 

 be complete. The section should be removed from the xylol as 

 soon as it is cleared; otherwise wrinkling occurs. 



(/) The section is placed upon a glass slide; a drop Canada 



