86 LABORATORY GUIDE IN BACTERIOLOGY 



2. Special study A. — Inoculate fermentation- tubes in 

 the same manner as in the two preceding groups. Ob- 

 serve the absence of gas-formation but note growth in 

 both arms. Compare the results with those of the colon 

 and intermediate groups. 



3. Special study B. — The staining of flagella. — Read 

 carefully in the textbook the methods of staining flagella. 

 To demonstrate the presence of flagella on B. typhosus, 

 the following method will give good results (LoefHer's 

 method) : 



a) Prepare the mordant. (What is a mordant ? See 

 the textbook.) 



Tannic acid (25^ aqueous solution) 10 parts 



Ferrous sulphate (saturated aqueous solution) . • • S P^rts 

 Fuchsin (saturated alcoholic solution) i part 



b) Prepare a number (six) of cover-slips by carefully 

 flaming them, and place them side by side on a piece of 

 filter-paper. (This paper must be burned after using). 



c) Place 4 or 5 loopfuls of water on a clean slide. 



d) Make a light suspension in this water of B. 

 typhosus from a 24-hour-old agar-culture, taking par- 

 ticular care to stir the suspension as little as possible. 



e) Place a loopful of water on each of the cover-slips. 

 /) Carry over a loopful of the suspension on the slide 



to one of the cover-slips, from this to second, from the 

 second to the third, etc. 



g)' Spread carefully and allow to dry in the air. 



h) Cover with the mordant. 



i) Heat over a small flame for ij minutes while 

 steam rises, or better heat for 5 minutes on a water-bath. 

 Replace the evaporated stain, to prevent its drying on 

 the cover-slip. 



