222 Theobald Smith 



gone beyond the three sugars noted excepting to test some 

 species in potato starch suspensions several years ago.*""' 



The source of the two gases CO2 and H may be explained 

 by the old formula of the text-books which splits one mole- 

 cule of grape sugar into two of lactic acid and these into one 

 of butyric acid and two each of CO2 and H. This formula 

 demands equal volumes of these gases. Scruel holds that the 

 molecule of glucose breaks up into one of formic, of acetic, 

 and of lactic acid with fixation of one atom of O. The gases 

 he derives from the direct decomposition of the newly formed 

 molecule of formic acid : 



CH,0, = CO., + H.,. 



As has been recently emphasized by Grimbert and stated 

 above, the process of fermentation varies from beginning to 

 end so that no single equation can express more than what is 

 going on at any one time. The same author ascribes this 

 continual change to a modification of the vitality of the fer- 

 ment organism brought about by the accumulation of harm- 

 ful products in the fluid. 



The rapid evolution of gas in the presence of one kind of 

 sugar and its slow accumulation in the presence of another 

 brings up the question whether or not an inverting ferment 

 comes into play in the slow fermentation. This question is 

 not approachable by the simple methods I have employed. 

 It is certainly a curious fact that one bacterium may produce 

 gas with almost equal rapidity in three sugars, another in two 

 and that these two may be, with one species, glucose and sac- 

 charose, with another, glucose and lactose. Thus the bacillus 

 of grouse disease produces gas in glucose, lactose and saccha- 

 rose with equal rapidity. 



Bacillus coli produces gas in glucose and lactose with equal 

 rapidity. Action on saccharose variable. 



* The action of bacteria on potato starch may be demonstrated by 

 cutting potatoes so that they fit rather snugly into test tubes. The film 

 of water between them and the glass imprisons any gas bubbles that 

 may be set free. In this way I noted the evolution of gas in several 

 species, among them Friedlander's bacillus. 



