5fi4 



Bulletin 167 



7. Milk. — The medium consisted of fresh eentrifuged milk, 

 titrated, filtered, and tubed, 10 ec. per tube. Sterilization was 

 effected by the intermittent method. 



Acid production. — Triplicate titrations of cultures and con- 

 trols were made after 1, 2, 4, 10, 20, and 46 days' incubation. 

 Five cc. of cultures and controls respectively were pipetted into 

 45 cc. of distilled water in Erlenmeyer flasks, 0.5 cc. of 1-100 

 phenolphthalein added, the mixture boiled 2 minutes and titrated 

 hot with N/20 sodium hydroxid. The averages of the three 

 titrations of cultures were compared with the averages of those 

 of the three control tubes, in order to obtain the percent of normal 

 acid or alkali produced at each time. The results obtained were 

 as follows : 



