THE NITRIFYING PROCESS AND ITS SPECIFIC FERMENT. 
125 
Appendix. 
Although in the experiments recorded above we have uniformly found that the 
pure nitrifying solutions yielded no growth in gelatine-peptone, we have by no means 
abandoned the hope of cultivating the nitrifying organism on this and possibly on 
other solid media. 
Thus, in our most recent experiments we find that on inoculating from the pure 
nitrifying solutions into broth, the latter develops after a considerable time (about 
twenty days at the ordinary temperature), a very characteristic growth, the liquid 
becomes turbid, a very thin whitish pellicle forms on the surface, and afterwards a 
considerable amount of glutinous deposit collects on the bottom, the whole liquid in 
fact becomes highly viscous and adheres to a needle in long strings. 
On microscopic examination, this growth is seen to consist of small bacilli, about 
1'5/r in length, and about '.5/1 in breadth, sometimes, however, forming threads (5'7/x 
in length) in which the divisions are generally not apparent, but sometimes the 
divisions were sufficiently discernible to show that these threads were really made up 
of four or five individuals hanging together, end to end. 
The accompanying drawing shows the appearance of the organism taken from a 
broth-culti vation. 
On inoculating from such a broth-tube into a second, it is found that the growth 
makes its ajipearance more rapidly than in the first, thus whilst tubes inoculated from 
the nitrifying solutions required about ten to twenty days before any conspicuous 
growth was developed, the broth-tubes inoculated from these exhibited the charac¬ 
teristic growth in about six to ten days. 
Although the microscopic appearance of the organisms in the broth-cultures thus 
somewliat departs from their appearance in the nitrifying solutions (compare figs. 1 and 
2), such slight divergence in form is by no means uncommon in the case of one and 
the same organism when growing in difierent media, and in previous communications 
on the morphological characters of micro-organisms we have frequently had to call 
attention to such differences of shape, which are in fact well recognised by all who 
are accjuainted with the nature of these low forms of life. We are, however, able to 
place beyond all dispute that the organisms growing in the nitrifying solutions (fig. 1), 
and those growing in the broth (fig. 2) are one and the same, for on inoculating the 
broth-growth into an ammoniacal solution, the latter (which, as we shall point out 
below, actually nitrified), again yielded the same cliaracteristic forms as were repre¬ 
sented in fig. f. Thus the acconqianying drawing shows the microscopic appearance 
