154 



LAURENCE F. FOSTER AND SAMUEL B. RANDALL 



registered by the two beef extract series is not explainable upon 

 such a basis for the same components were used in the preparation 

 of each. 



The remainder of the work has consisted of attempts to deter- 

 mine the causative factors in these reaction changes in order that 

 some procedure might be devised to obviate the effects produced. 



Although certain investigators have pointed out that the glass- 

 ware employed may exert an effect upon the reaction of the con- 



TABLE 4 

 Experiment I. Changes in reaction upon autoclaving and standing. (Beef 



infusion broth) 

 Composition: 



Distilled water 1000 cc. 



Chopped lean beef 300 grams 



Peptone (Parke, Davis & Co.) 10 grams 



NaCl 5 grams 



* Precipitate. 



tained media, experience in this laboratory has not borne out these 

 contentions. In the course of the present work it has almost 

 invariably been found that Ph determinations on a given medium 

 distributed in different tubes check closely. Consequently this 

 factor has at no time been seriously considered as even partially 

 contributory to the reaction changes encountered. 



It has been emphasized that in the very large majority of cases 

 the reaction change was in the direction of an acidity increase 



