504 l'.mj.KTiN 167 



thing less than — 30 Fuller's scale, and that growth is at least 

 slightly restricted in broth containing sufficient sodium hydroxid 

 to give a reaction of — 10. The second series of tubes was pre- 

 pared in the same manner as those already described, inoculated, 

 and placed in sealed glass jars containing a few cc. of 2% sodium 

 hydroxid. At the end of 10 days the jars were opened and the 

 tubes examined for growth. Those calculated to have a reaction 

 of : — 5 all showed healthy development, but no growth was ob- 

 served in tubes having a more alkaline reaction. Titration of a 

 control tube of the — 5 broth showed that the reaction had not 

 fallen below — 4 Fuller's scale. Tubes calculated to have a reac- 

 tion of — 10 tested — 6.1 and — 6.8 and those calculated to be 

 — 15 tested — 10 and — II. 



The third series was prepared in the same manner as the 

 second, but was incubated in Novy jars filled with air from 

 which the carbon dioxid had been removed by passing it through 

 wash bottles containing sodium hydroxid and calcium hydroxid 

 solutions respectively. The tubes were examined as well as 

 could be, without opening the jars, at the end of 7 days and 

 again at the end of 10 days. Growth was observed on both 

 occasions in tubes having reaction of — 5 but in no others. At 

 the end of 24 days the jars were opened and the tubes examined 

 critically for growth. All those calculated to have a reaction of 

 — 5 showed growth, but the stronger concentrations were in- 

 hibitory in all cases. Check tubes calculated to have a reaction of 

 — 5 were titrated and were found to react at from — 3 to — 5 

 Fuller's scale. 



Optimum reaction. — As a basis for determining optimum 

 reaction, nutrient bouillon having a reaction of o Fuller's scale 

 was employed. Portions of 100 cc. each were treated with the 

 requisite amount of hydrochloric acid or sodium hydroxid to 

 give reactions at intervals of 5 points of Fuller's scale. Material 

 was tubed, sterilized, and inoculated with a 2 mm. loop of broth 

 cultures, and placed in the incubator at 25 . The most vigorous 

 early growth occurred in tubes having reactions of +10 and 



