308 BACTERIOLOGY. 



causes the growth of the bacilli to cease, and the 

 rods degenerate. They may be cultivated in 

 various other nourishing media, such as blood- 

 serum, nutrient gelatine, and nutrient agar-agar 

 (Plate XIV., Fig. 2). 



The simplest way to obtain a culture of the 

 bacillus is to make a decoction of hay. The hay 

 is chopped into small pieces, and boiled with dis- 

 tilled water in a flask for a quarter of an hour ; it is 

 then filtered into a beaker, which must be covered 

 with a glass plate, and set aside in a warm place. 

 In two or three days the liquid swarms with the 

 bacilli, the spores of which exist in great numbers 

 in ordinary hay. A more sure method for obtaining 

 a pure cultivation is as follows : 



(a) Add only a small quantity of water to some 

 finely chopped hay, and set aside for four hours 

 at 36 C. 



(&) Pour off the extract, and dilute it to the 

 Sp. Gr. 1-004. 



(c) Boil gently for one hour in a bulb plugged 

 with cotton wool. 



(d} Set aside 500 ccm. of the extract at 36 C. 



In about twenty- four hours, as a rule, a pellicle 

 has commenced to develop upon the surface of 

 the liquid. If the reaction is definitely acid, 

 carbonate of soda solution must be added to the 

 decoction. 



