2O2 BACTERIOLOGICAL DIAGNOSIS. 



water) and must be entirely removed with the same 

 fluid before the section is mounted, or it will cause it to 

 fade. Clove oil is a very powerful decolorising agent, 

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

 from the bacteria. 



7. Eosin half a minute or more. This is a counter- 

 stain, 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 trans- 

 parent. 



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. 



(3). Method for bacteria which do not stain by 

 Gram's method ; suitable for sections of typhoid ulcers, 

 lymphatic glands containing plague bacilli, &c. 



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. 



