126 A MANUAL OF BACTERIOLOGY 



with the staining solution or immersed in it, and after 

 staining they are treated in the same manner, but in the 

 reverse order, viz. (1) distilled water ; (2) methylated 

 spirit ; (3) absolute alcohol ; (4) xylol. On being removed 

 from the xylol the slide is drained, a drop of xylol balsam 

 is then put on, and the section covered with a clean 

 cover-glass. Glass jars (Fig. 22) or wide-mouthed stop- 

 pered bottles, filled with the alcohol, xylol, etc., are 

 convenient for the treatment of paraffin sections, the slide 

 with the section upon it being immersed in the fluid, 

 which is used again and again. 



Section Staining 



When Gram's method is applicable it gives by far the 

 best results, and should generally be employed (p. 119). 

 If, however, the organisms are decolorised in Gram's 

 process some other method must be adopted. One of the 

 best is to stain for from ten minutes to thirty minutes in 

 carbol-thionine blue. Frozen sections may be immersed 

 in a watch-glass of the stain ; sections fixed to the slide 

 are flooded with the stain. Warming the staining solution 

 intensifies its action ; to do this the watch-glass or slide 

 is warmed on a piece of asbestos cardboard placed over 

 a Bunsen flame, or a penny may be heated in the Bunsen 

 and the preparation laid on it, the coin being re-heated 

 as often as required. The stain may be prevented from 

 flooding the slide by confining it between grease lines 

 as described for films (p. 122). After staining, the sections 

 are well rinsed in distilled water and then slightly de- 

 colorised by rinsing for half a minute or so with 1 per 

 cent, acetic acid in distilled water. They are then again 

 washed and passed as rapidly as possible through alcohol, 

 cleared in xylol, and mounted. Carbol-methylene blue 

 or Loffier's methylene blue may be used instead of the 



