5 2 BACTERIOLOGY. 



used in Ehrlich's method, which has been heated 

 to boiling-point. The fuchsine is removed from 

 the bacilli either by simply rinsing in water, in 

 alcohol, or in weak acid, according to the species, 

 and then the preparations are floated for a few 

 minutes on solution of methylene blue, rinsed in 

 water, dried and mounted. 



To stain flagella. Koch recommends floating 

 the cover-glasses on a concentrated watery solution 

 of haematoxylin. From this they are transferred 

 to a 5 per cent, solution of chromic acid or 

 to Miiller's fluid, by which the flagella obtain 

 a brownish-black coloration. The author has 

 succeeded in demonstrating and photographing 

 flagella, by staining with a drop of a saturated 

 solution of gentian violet in absolute alcohol. 

 Before the alcohol has time to evaporate the cover- 

 glass is rinsed in water, and then allowed to dry, 

 and finally mounted in balsam. A very intense 

 staining of the whole preparation results. 



(C) COVER-GLASS IMPRESSIONS. 



One of the most instructive methods for examin- 

 ing micro-organisms is to make what is called in 

 German a " Klatsch Prdparat" It enables us in 

 many cases to study the relative position of in- 

 dividual micro-organisms one to another in their 

 growth on solid cultivating media, and in some 

 cases produces the most exquisite preparations for 



