SYSTEMATIC AND DESCRIPTIVE. 22J 



METHODS OF STAINING COCCI. 



Cocci stain well with watery solutions of gentian-violet, 

 methyl-violet, fuchsine, methylene blue, and bismarck 

 brown. For examining cocci in liquids such as pus or 

 blood, or in cultivations in solid media, a little of the 

 material should be spread out on a cover-glass (page 48), 

 and stained with a drop or two of a watery solution of 

 fuchsine or methyl-violet. The former is especially recom- 

 mended for staining Merismopedia gonorrhoea. 



For a zooglcea, or pellicle of micrococci, Klein recom- 

 mends transference bodily to a watch-glass containing the 

 dye, leaving it there till deeply tinted, then taking it out 

 with a needle, washing in water, and then in alcohol till 

 excess of colour is removed. It must then be transferred 

 to a glass-slide, spread well out, and a drop of clove-oil 

 placed on it ; after a minute or two the clove-oil is drained 

 off, a drop of Canada balsam added, and covered with a 

 cover-glass.* 



Cocci in the tissues may be stained by immersing the 

 sections in an aqueous solution of gentian-violet, or 

 in aniline-gentian-violet solution, then rinsing in water, 

 decolorising in alcohol, treating with clove-oil, and pre- 

 serving in balsam (p. 58) ; or, after washing with alcohol, 

 they may be rinsed with water, and stained for half an 

 hour with Weigert's picrocarmine. From this they are 

 again removed to water, then to alcohol, clove-oil, and 

 Canada balsam. 



The method of Gram is much more satisfactory (p. 59, 

 Plate XII., Fig. 2). Sections should be examined with 

 and without a contrast stain. The after-stain most com- 

 monly employed is eosin. The sections after the process 

 of decolorisation should be placed in a weak alcoholic 

 solution of eosin (two or three drops of a concentrated 

 alcoholic solution added to a watch-glassful of alcohol), 

 till stained a delicate pink. They are then rinsed in 

 * Klein, Micro-organisms and Disease. 1885. 



