200 Theobald Smith 



sodium chloride in water) was also tried. Bacteria multiplied 

 so feebly in it, however, that it also was abandoned. 



The method finally settled on was to test each quantity of 

 bouillon prepared in the laboratory. If any failed to give 

 rise to gas in the fermentation tube it was set aside to be used 

 exclusively with these tubes. Unfortunatel)^ most of the gas- 

 production recorded in the tables following, took place in 

 bouillon containing traces of glucose since the work could not 

 be delayed. The difficulty has been partly overcome by keep- 

 ing a record of the quantity of gas formed in the same bouil- 

 lon to which no sugar was added. 



In searching through the literature of this subject I find that 

 the presence of glucose in bouillon has likewise been noted by 

 Pere' and by Pane® in its bearing on the products of bacteria 

 fermentation. The former considered it mainly in its relation 

 to the initial acidity of cultures, a relation, to which I had al- 

 ready called attention in 1890'. Pane sought to determine the 

 gas produced in peptone bouillon quantitatively by noting the 

 number and the size of the gas bubbles in bouillon-agar 

 when B. coli communis was mixed with fluid agar and this 

 rapidly hardened by cooling. He likewise determined the 

 amount of acid produced by the fermentation of this carbo- 

 hydrate. 



TYPES OF GAS PRODUCTION. 



In my experience with the cultivation of bacteria in the fer- 

 mentation tube a variety of hitherto unnoticed details have 

 come to light. In arranging and classifying these I find more 

 or less difficulty. It seemed perhaps the simplest plan to de- 

 scribe the gas production of a very common and much dis- 

 cussed species — Bacillus coli commii7iis — and then to refer 

 briefly to those species which belong to the same general 

 group. The observations of others so far as they bear on the 

 subject before us will be reviewed in a succeeding chapter. 



B. coli co7niminis. — It is not my intention to enter into de- 

 tail concerning the characters of this somewhat notorious in- 

 testinal species. At present its main differential characters 

 are accepted to be i, motility ; 2, prompt coagulation of milk; 

 and, 3, gas production in nutrient media containing lactose. 



