284 



Even tlie most slim}' Aërobucter tbnns produce quite different sub- 

 mei'ged cultures equally dispersed tlirougli the solution. 



The vigorously fermenting slime varieties of B. polymyxa produce 

 aceton, probably after the formula 



C.H„0. + 20, = C,H«0 + 3C0, + 3H,0. 



To the products of the anaërol)ic fermentation belong in parti- 

 cular aetliyl alcohol, 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 concentration and spread through the solution as Bad. aëi^ogenes. 

 Also in other res|)ects there is similarity between /?rtc^. a^ro(/<??je5 and 

 B. polymyxa, so that theie is cause to conclude to a real relationship. 

 Still there is a great difference in so far as a'érogenes can assimilate 

 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 carbohydrates, 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 pectinase, B. polymyxa 

 produces diastase, invertase 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 saltpeter. Urease is not secreted; 

 saltpeter is reduced to nitrile, not to nitrogen. 



As in absence of sugar the carbon cannot be withdra\yn 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 for- 

 mation 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 themselves unassimilable nitrogen compounds, 

 which enables the germs to change into small colonies, which 



