285 



renders the further growth after addition of tlie carbohydrate very 

 clear. 



Most sugars and polyalcohols are readily assinnilated by B. poly- 

 myxa. This we have ascertained for arabinose, glucose, levulose, 

 tnannose, galactose, cane-sugar, maltose, lactose, melibiose, rafifinose, 

 rhamnose, glycerin and inannite. On the other hand sorbite, dulcite, 

 erythrite and quercite are not attacked. It is x^ry notable that we 

 did not find any organic salt assimilable by this organism. 



The "sugar bacteria", to which 5. /?c>///my.i'a 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 cofiditions. At insufficient feeding with 

 carbohydrates, for example on broth agar, it grows as highly motile 

 rodlets, without slime wall; at copious feeding with carbohydrates, 

 as immotile rodlets with a thick slime wall ^). This circumstance 

 leads to the following experiment, only adapted to the variety of 

 B. polymyxa which produces voluminous slime and grows strongly 

 on malt-wort. 



The bacterium densely sown on cane-sugar-kaliumphosphate-agar, 

 containing but few nitrogen compounds, may form fairly large 

 colonies consisting, however, almost entirely of the strongly swollen 

 walls of the cells. By addition to the said medium of a few drops 

 of complete food, for example a little broth or malt-wort, con- 

 taining an excess of sugar, the slime walls grow surprisingly so 

 that the plate covers with a relatively thick slime coat. This slime 

 is built up of the sugars by one or more synthetically acting 

 enzymes, that might be named "cyteses" and should be considered 

 as the genes or factors of the cell-walls. 



This slime has the remarkable property of being able to become 

 itself a source of carbon food, but only at the moment when all 

 the cane sugar and all the assimilable nitrogen compounds have been 

 used. If at this time some such nitrogeti compound as ammonium- 

 sulphate or asparagin are brought on the slime coat of the plate, the 

 bacteria begin anew to grow and produce new protoplasm from their 

 own cell-walls. This leads to the peculiar consequence, that an aux- 

 anogram is produced sinking dee[) into the layer of slime. For, by the 

 growth the bulk of the bacteriais difninished, because the walls, which 

 chiefly consisted of water and were very voluminous, disappear 

 and are replaced by living protoplasm. So the appearance of the auxa- 



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



