THE NITRIFYING PROCESS AND ITS SPECIFIC FERMENT. 
127 
Nitric nitrogen was presumably absent; it could not, however, be tested for, owing 
to the insufSciency of the liquid available. 
As the ammoniacal solution originally contained about 11 parts of ammoniacal 
nitrogen (see analysis, page 123), and as some concentration of the liquid had taken 
place whilst in the Incubator, it is obvious that the above results indicate marked 
conversion of ammonia into nitrous acid. 
In the same way a bottle containing ammoniacal solution was inoculated from 
a similar broth cultivation on November 19, 1889, and placed in the incubator at 
24° C. On January 10 , 1890, this yielded strong reactions with diphenylamine, 
and also with sulphanilic acid. 
The duplicate bottle inoculated on November 4, 1889, but kept at the ordinary 
temperature (15-20° C.) has not yet nitrified. Nor has any nitrification yet taken 
place in a bottle inoculated from a gelatine culture on December 10, 1889. 
There is, however, nothing surprising in the retarded nitrification, which appears 
tlms, at best, to take place from broth or gelatine cultures, for there are many other 
instances of the physiological properties of organisms being modified by change of 
soil. It has, indeed, been frequently observed by one of us in the case of other 
fermentations, that the fermentative power of a particular organism towards a 
particular substance may be greatly modified by growing it in different media. This 
appears to have been already recognised by Fitz in his later work (‘ Berlin, Chem. 
Ges. Berichte,’ 1882, p. 878) in which the following very suggestive, but hitherto 
little recognised passage occurs :—- 
“ Die Fiihigkeit, Giihrung zu erregen, wire! ausser durch liohe Temperatur auch 
aufgehoben, wenn dem Spaltpilz sehr reichlich und andauernd SauerstoflP dargeboten 
wird. 
“ Wenn man, z. B., eine einzige Zelle in eine verhaltnissmilssig grosse Menge 
Kulturflussigkeit aussat, so wird die Gahrfahigkeit betrachtlich herabgestimmt und 
oft auch ganz aufgehoben. 
“ Ebenso verhiilt es sich wmnn man den Spaltpilz bei sehr reichlichem Luftzutritt 
viele Generationen hindurch in einer Kulturflussigkeit, in welclier er kelne Gahrung 
verursachen kann, kultivirt.” 
Brieger (‘Zeitsch. f Physiol. Chemie’, vol. 8, pp. 306-311) points out that the 
“pneumococcus” of Friedlander loses its pathogenic properties wlien cultivated in 
sugar solutions, and only regains them when again cultivated in the ordinary solid 
media 
Another very remarkable instance of the chemical properties of a micro-organism 
being altered by the medium in which it is cultivated, is exhibited by the well-known 
B. prodigiosiis, which on long-continued culture on gelatine or agar-agar loses its 
pigment-producing power, which can, however, be restored by cultivation on potatoes. 
In the present instance the nitrifying organism had l)een cultivated, as already 
mentioned, for nearly three years, in the dilute ammoniacal sohitions practically 
