1214 



dissolved in water with '/so 7o peptone or more, it grows, as said, 

 vigorously and produces colonies of the above nature, in tvlüch it 

 Ü always posslhle to detect some feir motile bacteria. The rodlets 

 now become somewhat longer and thicker than in the nitratating 

 state but for the greater part thej remain very short ; the ferment 

 has now changed into the poljtrophic form. 



In broth the same change takes place already on the second or third 

 day, at 30\, fairly rich cultures being obtained, whereby the broth beco- 

 mes distinctly turbid and is sometimes covered with a thin film, 

 perfectly resembling that of B. oligocarbophilus. In the liquid thin 

 rodlets and threads are found, many of which are moving. They 

 never ramify and their motility shows that they do not belong to 

 the family of the Actinomycetaceae, although their way of growing 

 might suggest it. Accordingly the statement in the manuals, that the 

 nitrate ferment may be recognised by its not growing and increasing 

 in pure culture in broth, is quite erroneous, only nitratation is 

 excluded. 



On broth-gelatin plates at room temperature the growth is at first 

 rather slow but very characteristic and finally fairly strong, where 

 by the gelatin (pule liquefies and much ammonium carbonate is 

 produced. 



On pui'e gelatin, dissolved in distilled water, with nutrient salts, 

 hardly any development \> visible, the ni(ratati\c power is never- 

 theless rapidly destroyed. 

 ^ The quantity of dissolved matter required to destroy this faculty, 



\ is extremely small. Media with Yso 7o ^^ substances such as 

 glucose, mannite. asparagin, peptone, tyiosin. natriumacetate, or 

 calciumacetate, cause a vigorous growth and total loss of the nitra- 

 tative function. With a much smaller amount of soluble organic 

 substance in the medium, for example that of common non-extracted 

 agar, the nitrate fenuent is able lo assimilate that slight quantity 

 without losing the faculty of nitratation. But under these circum- 

 stances weeks or months are required for the oxidation of the nitrite, 

 and many experiments fail altogether. Old dung, such as is found 

 in dung-heaps, does not destroy the faculty; vegetable juices, pressed 

 out from stems and roots of plants, convert the nitrate ferment 

 into the polytrophic, non-nitratative form, which conversion must, 

 under certain conditions, also take place in the soil. 



Humates in the culture liquids or plates, even in rather great 

 quantities, are not assimilated and cause no change in the nitratation. 



Addition of parafïinoil slackens the nitratation a little, but does 

 not at all prevent it. 



