Bacteria, their Nature and Function. 
375 
Photographs give an idea of the character of this organism in 
plate-, in streak- and stab-culture, and in microscopic specimens ; in 
these latter it is noticed that neither in size, nor arrangement, nor 
mode of division does this microbe show anything that would 
distinguish it from other species of staphylococcus ; its action on 
ui'ea is its chief distinguishing character, as it is capable of converting 
it into ammonium carbonate. 
At present it is well established that nitrogenous principles like 
indol, phenol, and ammonia are produced during the decomposition 
of albumin by proteus, Bacillus coli, and other putrefactive bacteria ; 
and, further, that substances, as indol, phenol, and the like, are, by 
the activity of certain other bacteria not yet sufficiently investigated, 
converted into ammonia. We have now traced the decomposition 
of albumin down to ammonia, and in this condition it is subjected 
in the soil to the action of the nitrifying bacteria — that is, bacteria 
which oxidise ammonia and convert it into nitrites and ultimately 
into nitrates ; these bacteria complete then the series of processes 
by which the nitrogen ultimately returns from where it started. 
It started as nitrates in the soil surrounding the roots of plants, 
and as nitrates it ultimately again finds itself in the soil ; first it 
had been used by the plant in order to build up its albumin, then 
as vegetable albumin it represents the food of animals ; in these it 
serves to build up the protoplasm of the animal body, from which it 
passes as food for carnivorous animals. The albumin of animals or 
plants becomes decomposed by putrefactive bacteria, the ultimate 
product of this, ammonia, becoming converted by the nitrifying 
bacteria of the soil into nitrites, and finally into nitrates. “ From 
earth to earth ” expresses the beginning and end of this wonderful 
migration and change ! 
Nitrifying Bacteria. 
Schloesing and Muntz were the first to show that the conversion 
of ammonia into nitrates in the soil is most probably caused by 
micro-organisms, but not till the researches of Warington, Wino- 
gradski, and P. Frankland were these micro-organisms isolated 
and more carefully experimented with. Warington, and particularly 
Winogradski, have shown that there are two species of bacteria 
which play an important part in these processes, one species 
converting ammonia into nitrites, the other converting these 
finally into nitrates. Some lantern slides of Winogradski were 
here exhibited, in which these two species are well shown ; the 
slides are of preparations of artificial cultivations, in which 
Winogradski has been extremely successful. These two species 
(the nitrous and the nitric organism) are minute rod-shaped or oval 
bacteria ; when in the act of dividing, they form short dumb-bells ; 
the nitrous organism is larger than the nitric, but both show forms 
which possess cilia, and which therefore are possessed of motility. 
Winogradski has by artificial cultivations obtained both these 
species in large quantities, and on testing them on liquids of 
