2i8 Theobald Smith 



In view of the presumable importance of gas production* 

 the question may be asked as to the permanence of this func- 

 tion. The permanent or temporary character, under cultiva- 

 tion, must largely decide for or against the position taken 

 above as to the fundamental importance of kinds of fermenta- 

 tion in the grouping of bacteria. The facts which I have col- 

 lected are necessarily meager since I have employed the fer- 

 mentation tube only for four years, and no other person has 

 thus far paid any attention to this subject. A few facts, how- 

 ever, bear on this point. I have not yet encountered any bac- 

 teria which have either gained or lost the gas-forming func- 

 tion under cultivation. In the colon group it does not appear 

 to vary at all from year to year. The same persistence was 

 observed in Proteus vulgaris. Of two varieties originally de- 

 scended from the same colony, one still actively liquefying gel- 

 atin, the other having lost this power almost absolutely, 

 both produce the same amount of gas in glucose and saccha- 

 rose bouillon. Recently I have noticed in one of the cultures 

 of B. cloacce, over a year old, a slight diminuition in the total 

 quantity of gas set free in saccharose bouillon. In glucose 

 bouillon the function seems to be intact. While, therefore, 

 the power of gas production may be slightly reduced quanti- 

 tatively it does not disappear. It likewise is, at least for 

 Proteus vulgaris, a much more permanent function than that 

 of secreting a liquefying ferment.f 



More or less related to an enfeeblement of the fermenting 

 power observed in the space of months and years in the same 

 culture, is an incapacity probably the result of an adaptation 

 to a parasitic existence. This is very well illustrated by the 



*I simply use this word as standing for types of fermentation which 

 need more careful examination by chemists than they have hitherto 

 received. 



t In opposition to my observations is one recorded by Arloing'. A 

 micrococcus septicus puerperalis (probably a streptococcus or a staphj'- 

 lococcus) produces no gas when fluids containing sugar are inoculated 

 from old cultures. When, however, young cultures twenty-four to 

 thirty-six hours old are used for inocculation, CO^ and H are given off 

 abundantly. Such a remarkable change of function must rest upon 

 some experimental error of the author. 



