134 BACTERIOLOGY. 



of the capsule which surrounds certain organisms, is to 

 prepare the cover-slips in the ordinary way, then cover 

 the layer of bacteria upon them with glacial acetic acid, 

 which is instantly poured off (not washed off in water), 

 and the aniline-water gentian-violet solution dropped 

 upon them; this is allowed to remain three or four 

 minutes, is poured off, and again a few drops added, 

 and lastly the slip is washed off in water. A very clear, 

 sharply-cut picture usually follows this method of pro- 

 cedure. 



Staining of Spores. — We have learned that one of 

 the points by which spores may be recognized is their 

 refusal to take up staining substances when applied in 

 the ordinary way. They may, however, be stained by 

 special methods ; of these the following will prove use- 

 ful : The cover-slip is to be prepared from the material 

 containing the spores in the ordinary way, dried, and 

 fixed. It is then floated, bacteria down, upon the sur- 

 face of a watch-crystalful of freshly prepared Koch- 

 Ehrlich solution of fuchsin. This is then held by its 

 edge with the forceps about 2 cm. above a very small 

 flame of a Bunsen burner, care being given that the 

 flame touches only the centre of the bottom of the crys- 

 tal. After a few seconds the crystal is elevated gradu- 

 ally until it is about 6 to 8 cm. above the flame, then 

 it is slowly moved down to the flame again, and this up- 

 and-down movement is continued until the staining 

 fluid begins to boil. As soon as a few bubbles have 

 been given off it is held aside for a minute or two and 

 the process of heating is repeated. When the boiling 

 begins, again the crystal is held aside for a minute or 

 two. The crystal is heated in this way for about five 

 or six consecutive times. When the fluid has stood for 



