THE MICROSCOPE AND MICROSCOPIC METHODS 59 



The above statements apply to frozen sections or to sections 

 imbedded in celloidin. Paraffin sections are preferably attached 

 to the slide with glycerin-albumen. The different steps in the 

 process follow in the same order. The stain may be poured on 

 the slide, or the slide may be placed in a large dish full of staining 

 fluid. (See page 44.) Celloidin sections may also be stained on 

 the slide. If the section be well spread and flattened thoroughly 

 with blotting paper, it will usually adhere to the slide, and is less 

 likely to wrinkle. It must not be allowed to dry. 



Gram's Method may be applied to the staining of sections 

 of tissues as well as to smears upon cover-glasses. 



(a) Place the section in aniline-water gentian violet, one to 

 five minutes. 



(b) Rinse briefly in water.- 



(c) Iodine solution (see page 45), one and one-half minutes. 



(d) Alcohol, until decolorized to a faint blue-gray. 



(e) Xylol. 



(/) Mount on a slide in balsam. 



Weigert's Modification of Gram's Method, or Weigerfs 

 Stain for Fibrin. (a) Place the section in aniline-water gentian 

 violet solution, five minutes or more. 



(b) Wash briefly in water. 



(c) Place the section upon a slide by means of a section lifter; 

 having straightened it carefully, absorb the water with blotting- 

 paper. 



(d) Gram's solution (see page 45) one to two minutes. 



(e) Absorb the iodine solution with blotting-paper. 



(/) Add aniline oil, removing it from time to time with blotting- 

 paper, and adding fresh aniline oil until the color ceases to come 

 away. (Aniline oil serves in this connection both to decolorize 

 and to dehydrate. It absorbs the water rapidly and efficiently. 

 However, on account of its decolorizing tendency, it must be re- 

 moved before the specimens can be mounted permanently.) 



(g) Add xylol; remove it with blotting-paper; and add fresh 

 xylol several times, in order to extract the last trace of aniline oil. 



