14 



Acid vs. Alkaline Beef Broth. 



The following experiments were undertaken in 1899 to determine, 

 approximately, the limits of growth of Ps. liyacintki in acid and alka- 

 line media. As a standard for comparison, I made use of a peptonized 

 1 : 2 beef broth neutralized to phenolphthalein by caustic soda, and well 

 adapted to the growth of this organism. Portions of this stock were 

 then acidified with varying quantities of malic acid, and others were 

 rendered alkaline to phenolphthalein by an excess of caustic soda. Each 

 test tube was of resistant glass, contained exactly 10 c. c. of the fluid to 

 be tested, and was exposed to the same temperature. Except —80, all 

 were inoculated June 11, from tube 8, May 14, a coconut culture, the 

 growth of which had been delayed for some weeks in a U tube (nitro- 

 gen). Each tube received a very large number of germs and approxi- 

 mately the same number, i. e. , a scant 2 mm. loop of the fresh 3^ellow 

 slime. Except —80, all of the cultures were carried through in 

 duplicate. The approximate date of the clouding (temperature 25 "^ to 

 30" C.) is shown in the following table, in which 0, is "clear," -|-, 

 "feebly clouded," and -|- + , "very feebly clouded." 



