154 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



As soon as about two litres of gas had been collected a 

 sample of about 500 c.c. was taken for analysis. The remainder 

 of the gas was swept out through the three-way tap by raising 

 the measuring bottle, and the apparatus then arranged as before 

 for the collection of a fresh quantity of gas. 



At the close of about fourteen days the flask was removed 

 from the incubator, and a culture made on agar, which was 

 examined and in every case found to give the usual tests for 

 normal B. coli communis, or other organism studied. The 

 solution was then measured, and aliquot portions removed 

 for the estimation of the various constituents. 



These products comprised : — 



Lactic acid. 

 Succinic acid. 

 Acetic acid, 

 Ethyl alcohol. 

 Formic acid, 

 Carbon dioxide, 

 Hydrogen. 



The effect of various nitrogenous products serving as 

 sources of nitrogen for the organism was also studied. It 

 was found that Witte's peptone was the best source of nitrogen 

 to employ, as the products of its decomposition are not 

 sufficient to interfere with the estimation of those produced 

 from the special compound under examination. 



The general method of preparation of the medium imder 

 examination was as foUows : 10 grams of Witte's peptone 

 were boiled with tap water, 20 grams of the sugar or other 

 compound to be examined were added, together with 10 

 grams of pure calcium carbonate, the whole being made up 

 to one litre ; in some cases 2 grams of calcium phosphate 

 were added, but no beneficial effect could be observed. Harden 

 found that glucose yielded chiefly Isevo-lactic acid together 

 with 5'25 per cent, of the inactive form ; fructose, arabinose 

 and galactose behave similarly. On the other hand, mannite 



