BOUILLON OR BEEF-TEA. 37 



Then stir in the salt and add the rest of the 

 water. Boil for fifteen minutes ; test the reaction with litmus- 

 paper (it is always slightly acid because of the acid in the 

 meat-extract), and alkalinize with a saturated solution of 

 sodium bicarbonate or sodium hydrate, adding the solution 

 drop by drop until the bouillon is neutral or faintly alkaline. 

 The mixture should be stirred constantly. As soon as the 

 mixture is cold it is ready to be filtered. It should never be 

 filtered while hot, as it will be cloudy because of the precipi- 

 tated meat-salts. Fold the filter-paper and moisten it with 

 hot water before using. Pour the bouillon on the paper 

 slowly so as not to break the filter. If the filtrate is cloudy, 

 it should be filtered again until it is perfectly clear. If the 

 solution is too alkaline, it will be cloudy. The alkalinity 

 can be reduced by the addition of a little hydrochloric acid ; 

 but it is better not to do this, as too much manipulation is 

 very apt to interfere with the usefulness of the medium. 

 Enough water should be added to replace that lost by evapo- 

 ration. 



The liquid is then filled into sterile test-tubes, about ] c.c. 

 in each tube, and each tube plugged with a cotton stopper. 

 The tubes, previously placed in wire test-tube baskets (Fig. 

 .1(5), are sterilized in the steam sterilizer for fifteen minutes 

 on each of three successive days. This sterilization must 

 be carried out carefully, in order to prevent contamina- 

 tion from any bacteria which may have been contained in the 

 bouillon. When completed, the bouillon should be of a light 

 straw color. 



This method is subject to such changes and modifications 

 as may appear necessary or desirable. The proportions of 

 the various ingredients may be changed, but none of these 

 can be omitted or displaced. The beef-stock is prepared 

 from the meat itself, as follows : place 500 grams of finely 

 chopped lean beef in 1000 c.c. of clean water, and allow this 

 to stand on ice for twenty-four hours. The liquor is then 

 decanted and the beef thoroughly expressed through a clean 

 white cloth, and sufficient water added to make 1000 c.c. 

 Then the peptone and salt are added, and the bouillon is fin- 

 ished as already described. 



