106 A MANUAL OF BACTERIOLOGY 



removed with filter-paper and the sections are flooded 

 with anilin oil two or three times. This removes the 

 colour and dehydrates. The anilin oil is removed by 

 flooding two or three times with xylol. 



Thionine blue may be used for Gram's method, the 

 carbol solution being employed (No. 5, p. 100). Sections 

 are stained for two or three minutes, then treated with 

 an iodine solution somewhat stronger than Gram's (200 

 parts of water instead of 300 parts). The sections, after 

 remaining in this for one to two minutes, are decolorised in 

 alcohol containing 1 per cent, of acetone (methylated spirit 

 does very well), and subsequently treated as in Gram's 

 method. 



The Staining of Film Specimens 



To stain films, smear, and impression preparations, 

 the film is flooded after fixing with a drop or two of the 

 solution, or the preparation, if a cover- glass, may be 

 floated, film side down, on the solution contained in a 

 watch-glass ; if it should sink it makes little difference. 

 Various baths or pots can be obtained for staining slides. 

 Warming intensifies the staining properties of all staining 

 solutions, and may be necessary if deep staining is required 

 or if the temperature of the laboratory be low (see also 

 p. 110). When stained sufficiently, the preparation is 

 rinsed in a beaker or tumbler of water, or in a fine stream 

 of water, preferably distilled, to remove the superfluous 

 colour, after which it is dried and mounted in a drop 

 of solution of Canada balsam in xylol. The preparation 

 may be dried either by gentle warming over the Bunsen 

 flame after the film has been blotted with filter-paper, or 

 the film may be allowed to dry spontaneously in the air, 

 in which case it should always be set up on edge to drain. 

 The preparations must be completely dried before being 

 mounted in balsam. 



