372 
Bacteria , their Nature and Function. 
to 248 millions per cubic centimetre, and in the third twenty-four 
hours to 1,184 millions per cubic centimetre. (1 cubic centimetre 
= •061 cubic inch.) 
A point of interest is the motility exhibited by certain bacteria. 
In some species most, in others comparatively few, individuals show 
active locomotion, spinning round and darting to and fro ; in many 
other species no motility is observed. In the motile species it is 
known that this motility is due to the presence and active motion 
of cilia or flagella, and these have been seen and photographed in 
former years in some of the larger forms, but only within recent 
years has it been possible, by means of new methods (Loftier), to 
actually demonstrate in the smallest forms these flagella, and here 
the remarkable facts have been shown that while some possess only 
one flagellum at one end, in other species the bacillus possesses a 
bundle of them, or is covered with the flagella on its whole surface. 
Photographs were shown of the flagella, one possessing two flagella 
at one end ( Spirillum volutans), the other (cholera bacillus) one at 
one end, and the third (typhoid bacillus) covered with quite a 
number of flagella. 
A not less interesting point is the formation of spores : the only 
trustworthily ascertained mode of spore formation is that which is 
called endospores ; a bacillus at a certain phase develops in its 
protoplasm a minute glistening granule ; this increases in size and 
becomes oval, while the rest of the substance of the bacillus becomes 
pale, swells up, and gradually degenerates and disappears, leaving 
the fully formed oval bright spore free. These spores offer great 
resistance to temperature, chemical obnoxious substances, drying, 
Ac., so that even after long periods and various adventures, when 
again brought under proper and suitable conditions, they are cap- 
able of germinating into the bacilli. These then grow and divide, 
and continue to do so, producing new crops. Non-sporing bacteria 
are for this reason more liable to succumb in the struggle for exist- 
ence, although many species of non-sporing bacilli have such a vast 
power of multiplication and are so little selective in their require- 
ments that they manage to keep their crops perpetually going ; 
some notorious putrefactive cocci and bacilli belong to this class. 
Having now mentioned the essential features in the morphology of 
bacteria, I proceed to give a short summary of some of the most 
important activities which bacteria exhibit. 
Bacteria causing Decomposition op Albumin. 
Foremost in importance and vastness of result is the action which 
certain species of bacteria have on albuminous matter, an action 
which is termed 'putrefactive decomposition of albumin, animal or 
vegetable. All organic matter when deprived of life is resolved into 
similar compounds, is broken up into lower nitrogenous principles, 
like leucin, tyrosin, indol, phenol, <fcc., of which the ultimate products 
are ammonia, nitrites, and nitrates. The plant, it may be said in a 
general way, builds up albuminous matter from nitrates. This 
