CHANGES PRODUCED BY A SAPROPHYTIC ANAEROBE 395 



The results indioatod that the curve was (hie not to propionic 

 acid but rather to a mixture of acetic, buytric and perhaps to 

 valerianic acid. We felt, however, that work of this sort led to 

 rather uncertain results, since we were able to simulate almost 

 any acid curve desired by mixtures of other acids in the proper 

 proportions. 



The refractionation method proposed by Wolf and Telfer was 

 not exhaustive enough to obtain various acids in a form suf- 

 ficiently pure for accurate tests. 



The fractional distillation of the cultures was completed in an 

 attempt to find differences wide enough to be of diagnostic value, 

 even though the acids present were not completely identified. 



DISCUSSION OF RESULTS 



An examination of table 4 will give an idea of the action of these 

 orgainisms upon media rich, both in protein and carbohydrates. 

 The cultures were very closely related in all respects in their bio- 

 chemical reactions. 



In most respects the quantitative results compare favorably 

 with the qualitative results, but unfortunately do not give much 

 additional information. Those showing large amounts of gas 

 and acid in fermentation tubes, and Hiss serum water media con- 

 taining the various carbohydrates and grown over phosphorus in 

 an anaerobic jar, also show quantitatively larger amounts of gas 

 and acid when grown in vacuum. It was impossible to obtain 

 duplicates which checked exactly. Variation is inherent in all 

 bacteriological work and the results obtained in this work check 

 about as closely as those in many other bacteriological deter- 

 minations. 



Probable error. Two series of cultures were set up to determine 

 the probable error. One series of five bottles containing two 

 percent peptone-water after four days contained the following 

 amounts of gas 92. 86, 61, 73, and 87 cc, respectively. A series 

 of six bottles containing whole milk after two days contained the 

 following amounts of gas 237, 243, 232, 203, 196, 186 cc, respec- 

 tively. By using the formula: 



E = 0.6745Y 



A^ (iV - 1) 



