13 



To the products of the anaërobic fermentation belong in particular aethyl al- 

 cohol, with traces of acetic acid and formic acid beside some other products, such as 

 butylic glycol, in small quantities. 



The less slimy varieties of B. polymyxa can only live in food of lower concentra- 

 tion and spread through the solution as Bact. aërogenes. Also in other respects there is 

 similarity betvveen Bact. aërogenes and B. polymyxa, so that there is cause to conclude 

 to a real relationship. Still there is a great difference in so far as aërogenes can assimi- 

 late many organic salts, a power quite absent in B. polymyxa. 



Nutrition. 



For the investigation of the substances which can be assimilated by B. polymyxa, 

 the auxanographic method is very convenient, particularly in relation to the car- 

 bohydrates, B. polymyxa being a real „sugar bacterium", which produces much 

 cell-wall matter, which makes the auxanograms very distinct. In judging the latter 

 it should be kept in view that, beside p>ectinase, B. polymyxa produces diastase, in- 

 vertase and emulsine. In presence of sugar various nitrogen compounds are assimilable 

 of which, however, only nitrogen is taken up. We preferently used peptone, asparagine 

 ureum, ammonium sulphate and saltpetre. Urease is not secreted; saltpetre is reduced 

 to uitrite, not to nitrogen. 



As in absence of sugar the carbon cannot be withdrawn from nitrogen compounds, 

 such as peptone and asparagine, the growth, even on broth-bouillon-agar is but 

 slight and is a criterion for the quantity of sugar present. Hence, if on this medium 

 B. polymyxa is densely sown, only small, hardly visible colonies grow, consisting, 

 however, of bacteria with abundant protoplasm and commonly motile. If on such a 

 culture an assimilable carbohydrate is locally distributed, vigorous growth ensues, 

 chiefly reposing on slime formation and a distinct auxanogram results, demarcated 

 by the limit of diffusion of the substance. It is in fact the presence of a small amount 

 of complete food at the starting of the experiment, together with excess of by them- 

 sèlves unassimilable nitrogen compounds, which enables the germs to change into 

 small colonies, which renders the further growth after addition of the carbohydrate 

 very clear. 



Most sugars and polyalcohols are readily assimilated by B. polymyxa. This we 

 have ascertained for arabinose, glucose, levulose, mannose, galactose, cane-sugar, 

 maltose, lactose, melibiose, raffinose, rhamnose, glycerin and mannite. On the other 

 hand sorbite. dulcite, erythrite and quercite are not attacked. It is very notable that 

 we did not find any organic salt assimilable by this organism. 



The „sugar bacteria", to which B. polymyxa belongs, produce from carbohydrates 

 much more visible cell-wall substance than protoplasm, if the carbohydrates exceed 

 the nitrogen food and vice versa. 



Hence, B. polymyxa may be found, as was observed above, in two microscopically 

 greatly different conditions. At insufficiënt feeding with carbohydrates, for example 

 on borth agar, it grows as highly motile rodlets, without slime wall; at copious feeding 

 with carbohydrates, as immotile rodlets with a thick slime wall i). This circumstance 



») Medici give to the cell-wall of bacteria the singular name of „capsule". 



