APPENDIX 



IT is proposed to add one or two notes on certain technical 

 points in bacteriological work, with a view to assisting those 

 medical men not able to obtain the advantages of a well-equipped 

 laboratory, and yet desirous of occasionally attempting some 

 practical bacteriology. 



i. General Examination. All fluids may be examined for bac- 

 teria in two chief ways: 



(a) A small quantity may be placed on a cover-glass or slide, 

 dried over a lamp or bunsen flame, and stained with aniline dyes 

 for a few minutes. It is then ready for microscopic examination. 

 It is obvious that the result will generally be a mixture of bacteria, 

 for which differentiating stains may be used (Gram, Ziehl-Neel- 

 sen, etc.). * 



() A minute drop of the suspected fluid may be added to 

 various fluid media (broth, liquefied gelatine, etc.) and then 

 plated out upon small sterilised sheets of glass. In the course 

 of two or three days the contained bacteria will reveal themselves 

 in characteristic colonies, which may be examined, and if possible 

 sub-cultured, and carefully studied. 



Double- Staining Methods. These are various, and are used 

 when it is desired to stain the bacteria themselves one colour, 

 and the matrix or ground substance in which they are situated 

 another colour. Three of the commoner methods are those of 

 Ehrlich, Neelsen, and Gram. They are as follows: 



Ehr lie fi s Method. " Five parts of aniline oil are shaken up 

 with 100 parts distilled water, and the emulsion filtered through 

 moistened filter paper. A saturated alcoholic solution of fuchsine, 

 methyl-violet, or gentian-violet is added to the filtrate in a watch- 



22 



337 



