iga CLINICAL BACTERIOLOGY AND HEMATOLOGY 



6. Absolute alcohol or methylated spirit — until no more colour 

 comes out. This step is best carried out as follows : Hold the 

 slide by one end, keeping the fingers clean by using a duster or 

 pair of dissecting forceps, and pour a little spirit on the section ; 

 rock it gently from side to side and notice the clouds of colour 

 which it takes up. After a little time pour off the spirit and add 

 a fresh lot ; repeat the rocking, and pour off again. Do this 

 until the spirit comes away quite clean, and does not take up any 

 colour from the section. This may take a long or short time, and 

 no definite rules can be laid down. 



In some cases decolorization can be carried out best by the use 

 of clove oil. This is applied when the section is wet with absolute 

 alcohol (for it will not mix with water), and must be entirely 

 removed by the same fluid before the section is mounted, or it will 

 cause it to fade. Clove oil is a very powerful decolorizing agent, 

 and requires careful use, or the colour may be removed from the 

 bacteria 



7. Eosin — half a minute or more. This is a counterstain, and 

 is used to demonstrate the structural elements, which are not 

 coloured by the gentian violet. It may be omitted in some cases. 



8. Absolute alcohol — two lots (to remove the water). 



9. Xylol — -two lots, or until the section becomes transparent. 



10. Balsam and a cover-glass. 



This method of staining is very easy of application, and the 

 results are exceedingly beautiful. Bacteria which take the stain are 

 coloured blue or violet, and actively dividing nuclei and keratin are 

 stained in the same way, while all other structures are stained pink. 



III. Method for bacteria which do not stain by Gram's method, 

 suitable for sections of typhoid ulcers, lymphatic glands containing 

 plague bacilli, etc. 



The problem before us in this case is not at all easy of solution . 

 In the first place, the stains which colour the bacteria also colour 

 the tissues, especially the cell nuclei; the bacteria are easy to 

 stain, but it is difficult to stain a section in which there is good 

 differentiation. In the second place, the stains which are used for 

 bacteria are all soluble in alcohol : but alcohol is used to dehydrate 

 the sections. The following method will be found to serve fairly 

 well in most cases, though it requires a certain amount of practice 

 for its successful accomplishment. 



I, 2, and 3. Xylol, alcohol, and water, as before. 



4. Stain in carbol thionin for ten minutes or a quarter of an hour. 



