NUTRIENT MEDIA 



101 



and products to osmose outward and be absorbed by the animal, 

 while the animal fluids percolate into the sac. There are several 

 very ingenious ways of making these sacs, but the details are too 

 elaborate to be described here. 



BOUILLON. 



Bouillon or broth is the most useful of all the nutrient media, 

 since it is not only used as a liquid medium, but by the addition 

 of gelatine, or agar, it is converted into solid 

 media. 



There are two methods of making 

 bouillon. 



Method i. 



Take 500 grams of lean beef free from 

 all fat, chop it fine and cover with 1,000 

 c.c. of water, shake and place on the ice 

 over night. Then squeeze the fluid out of 

 the meat by means of a cloth, and supply 

 enough water to make a litre. Inoculate 

 this meat juice with a fluid culture of the 

 colon bacillus for the purpose of ferment- 

 ing the meat sugar. For this purpose the 

 inoculated juice is allowed to stand at 

 room temperature over night. Bring to a 

 boil and add 



10 grams of Witte's peptone. 

 5 grams common salt. 



FIG. 27. Kitasato fil- 

 ter for filtering toxins. 

 (Williams.) 

 Weigh the saucepan and contents and heat 



to 60 C. Supply the water lost by evaporation. Neutralize either 

 by adding sufficient sodium hydrate, 10 percent solution, until red 

 litmus paper is colored a faint blue, or else titrate 10 c.c. of the 

 mixture with a decinormal solution of sodium hydrate, using phenol- 



