1920] 
CHAMBERS—BACTERIAL INHIBITION BY METABOLIC PRODUCTS 265 
TABLE IV 
GROWTH puc ae rea ION CONCENTRATION OF BACILLUS COLI AT 
° ©., DEXTROSE BOUILLON, REINOCULATED 
Culture A B C 
Treatment None Sterilized Acidity adjusted 
Bacteria Bacteria Bacteria 
Hours per ce. Pu per cc. Pu per cc. Pu 
0 275,000 Del 286,000 5.1 261,000 7.9 
12 11,400 5.0 15,200 4.9 280,000,000 5.5 
24 7,200 5.0 3,800 4.9 |320,000,000 | 5.5 
36 3,600 4.9 650 4.9 340,000,000 5.3 
48 530 4.9 75 4.9 
60 30 4.9 2 4.9 264,000,000 5.1 
84 0 4.9 0 4.9 104,000,000 | 5.1 
108 89,000,000 5-1 
132 57,000,000 5.1 
156 9,500,000 5.1 
180 i 660,000 | 5.1 
204 36,600 5.1 
228 5,400 5.1 
252 280 5.1 
300 0 5.1 
hibitory substance which was destroyed by sterilization or 
inactivated on standing. The evidence of these results is against 
an “autotoxin” theory and points toward the hydrogen ion 
concentration as the predominating inhibitory factor in the 
experiments cited. 
'The balance of the experimental work concerns the relation 
of hydrogen ion concentration to inhibition. To counteract 
the influence of acid and alkali produced during growth, and 
thus to study their action by comparison, two cultures were 
observed in which the acid or alkali formed was neutralized at 
frequent intervals. 'The media used was the same as that 
reported in table 1, one culture of plain bouillon and the other 
of 1 per cent dextrose bouillon, 500 cc. each in 1000-cc. flasks. 
The acid produced in the dextrose culture was neutralized at 
12-hour intervals by the addition of N/1 NaOH and the hy- 
