EXPERIMENT STATION BULLETINS. 



299 



the required acidity was longer delayed and that it did not respond with readiness 

 to the usual management of the lactic acid starter. This was experienced the day 

 the inflation of the curd was first noticed. Upon the addition of the rennet with 

 the formation of the curd, the spongy condition appeared. In a separate vat in 

 which there was none of this "gassy" starter, the curd was compact and contained as 

 few gas holes as commonly present. This indicated conclusively that the causal agent 

 of this specific case of gassy curd was isolated. 



Our next elfort was to ascertain the rapidity with which this bacillus was able 

 to produce gas. For this purpose a glass tube an inch in diameter was bent into a 

 U form, making the arms about eighteen inches to two feet in length. One arm was 

 then hermetically sealed at the end and drawn out to a fine point to facilitate the 

 adjustment of a rubber tube later in the process. This tube was then so filled with 

 milk that only the hermetically sealed end or arm contained milk, leaving the other 

 to receive the milk on the formation of gas. After plugging the open end with cotton 

 wool and sterilizing in the steam bath as usual, the tube was inoculated and placed at 



Fifi-. 1. 



the room temperature (70 degrees F.). Gas was very noticable in twenty-four hours, 

 but from twenty-four hours after inoculation to seventy-two hours after inoculation, 

 gas elimination was very rapid, so that the amount formed was sufficient to nearly 

 press the milk out of the closed end of the tube. Fig. 1 illustrates this fermenta- 

 tion. This operation was repeated several times with uniform results. Precipitation 

 of the casein occurred in no case until several daj's after inoculation, yet the milk 

 was markedly acid, falling short of sufficient to throw down the casein. When these 

 tubes were placed in an incubator at 3714 degrees C. (98 degrees F.), within eighteen 

 to twenty-four hours the maximum (about) amount of gas was produced and the 

 casein also precipitated. This points to very rapid work on tlie part of this micro- 

 organism at the time when the milic is warmed to hasten the necessary amount of 

 acidity, and explains the rapid formation of gas in the curd. Upon testing the acidity 

 of a milk culture which had stood for twenty-six days, using phenol-phthalein as 

 indicator, there was .2!) per cent acid calculated as lactic acid. Upon adding litmus 

 to milk cultures tlie reaction was acid at first and continued to remain acid for six 



