LABORATORY AND GREENHOUSE STUDIES. 109 



Check tubes of these media were treated as follows : 



No. 1+acid =bright salmon pink. 

 No. l+alkali=deep blue. 

 No. 2+acid =bright .salmon pink. 

 No. 2+alkali=no change. 



In the first medium the culture grew well and produced acid, as 

 shown from the change in the color of the light reddish-purple check 

 to the bright pink cultures, Bacillus coli acting in the same way as 

 the coconut cultures. In most cases the color subsequently became 

 bleached and in the upper part a distinct blue (after 17 days). These 

 tubes tested with neutral litmus paper indicated an alkali formation, 

 as the change in color of the culture from bright pink to blue also 

 indicates. 



The reaction in medium No. 2 was unsatisfactory. In the check 

 tubes as in the cultures the blue color precipitated in the form of 

 fine particles. This precipitate remained blue in the check, but 

 became a distinct purple in the cultures, and in 17 days was bleached 

 almost wliite. A distinct, though not strildng, change from deep 

 blue to purple took place in the color of the precipitate. This change 

 would suggest some acid formation, although the medium is not 

 supposed to permit of acid formation. The reduction of the litmus 

 is the only striking part of the reaction in medium No. 2. 



BEEP BOUILLON OP VARIOUS DEGREES OP ACIDITY. 



Table XXVI gives the results of four experiments, showing very 

 little constant difference in the growth of cultures in beef-bouillon 

 media of various degrees of acidity or alkalinity. Any sort of 

 bouillon from —12 to +30 on Fuller's scale seemed to furnish" the 

 means for luxuriant growth of the organism. The cultures show a 

 tendency to clear sooner at +23, +25, and +30 than at the lower 

 degrees of acidity. 



228 



