STAINING OF FLAGELLA 111 



distilled water. A few drops of the stain are placed 011 a film, previously 

 dried and fixed by heat, and the preparation is steamed for a few seconds over 

 a flame. The staining solution is washed off with a 20 per cent, solution 

 of copper sulphate, the preparation (without being washed in water) is dried 

 between filter-papers, and when thoroughly dry is mounted in balsam. The 

 capsules of pneumococci growing in a fluid serum medium can be readily 

 demonstrated by this method ; in the case of solid cultures films should 

 be made without any diluent, or a drop of fluid serum should be used. 

 The method is easily applied, and gives excellent results. 

 (c) Richard Muir's Method (modified). 



1. The film containing the bacteria must be very thin. It is dried 

 and stained in filtered carbol-fuchsin for half a minute, the preparation 

 being gently heated. 



2. Wash slightly with spirit and then well in water. 



3. Place in following mordant for a few seconds : 



Saturated solution of corrosive sublimate . . .2 parts. 



Tannic acid solution 20 per cent 2 ,, 



Saturated solution of potash alum . . . 5 ,, 



4. Wash well in water. 



5. Treat with methylated spirit for about a minute. 

 The preparation has a pale reddish appearance. 



6. Wash well in water. 



7. Counterstain with watery solution of ordinary methylene-blue for 

 half a minute. 



8. Dehydrate in alcohol, clear in xylol, and mount in balsam. 



The bacteria are a deep crimson, and the capsules of a blue tint. The 

 capsules of bacteria in certain culture media may be demonstrated by 

 this method. 



The Staining of Flagella. The staining of the flagella of 

 bacteria is the most difficult of all bacteriological procedures, 

 and it requires considerable practice to ensure that good results 

 shall be obtained. Many methods have been introduced, of 

 which the two following are very satisfactory : 



Preparation of Films. In all the methods of staining 

 flagella, young cultures on agar should be used, say a culture 

 incubated for from ten to eighteen hours at 37 C. A very 

 small portion of the growth is taken on the point of a platinum 

 needle, and carefully mixed in a little water in a watch-glass ; 

 the amount should be such as to produce scarcely any turbidity 

 in the water. A film is then made by placing a drop on a 

 clean cover-glass and carefully spreading it out with the needle. 

 It is allowed to dry in the air, and is then passed twice or 

 thrice through a flame, care being taken not to over-heat 

 it. The cover-glasses used should always be cleaned in the 

 mixture of sulphuric acid and potassium bichromate described 

 on page 94. 



