NUTRIENT GELATIN 111 



tate. This may be due either to excess of alkalinity or to 

 incomplete precipitation of the albumin. The former may 

 be corrected with dilute acetic or hydrochloric acid, and the 

 bouillon again boiled, filtered, and sterilized; or, if due 

 to the latter cause, subsequent boiling and filtration usually 

 result in ridding the bouillon of the precipitate. 



Another modification now generally employed is in the 

 substitution of meat-extracts for chopped meat in making 

 the bouillon. Almost any of the meat-extracts of com- 

 merce answer the purpose, though we usually employ 

 Liebig's. It is used in the strength of from two to four 

 grams to the litre of water. Peptone and' sodium chloride 

 are added as in the bouillon made from meat-infusion. 

 The advantages of meat-extract are: it takes less time; 

 affords a solution of more uniform composition if used in 

 fixed proportions; and in general use gives results that are 

 equally as satisfactory as those obtained from the employ- 

 ment of infusion of meat. The disadvantage is the possible 

 presence of antiseptics or preservatives. 



NUTRIENT GELATIN. 



For the preparation of gelatin the bouillon is first made 

 in the way given, except that its reaction is corrected after 

 the gelatin has been completely dissolved, which occurs 

 very rapidly in hot bouillon. The reaction of the gelatin of 

 commerce is frequently more or less acid, so that a much larger 

 amount of alkali is needed for its neutralization than for 

 other media. It is possible, however, to obtain from the 

 makers an excellent grade of gelatin from which practically 

 all free acid has been carefully washed. The gelatin is 



