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VITAL MANIFESTA TIONS OF BA CTERIA 2 1
velopment of bacteria and an acid reaction. 'No bubbles of gas
were seen to be ascending through the solution, or to have
accumulated upon its surface, as is frequently the case in such
cultures. Hereupon the end of the escape-tube was made to
dip into lime-water, in which the smallest quantity of CO^ escap-
ing from the flask would be readily detected by the cloudiness
occasioned by the formation of the carbonate of lime, but after
twelve hours no cloudiness had appeared. I then heated the
flask, in order to drive out any carbonic acid possibly formed
the lime-water, however, still remained clear. I repeated this
experiment with an apparatus for collecting the gas over mer-
cury. In a culture in which 1.75 grams of lactic acid were pro-
duced, only one little bubble of gas was collected, which might
as well have been caused by an imperceptible rise in the temper-
ature of the incubator as by actual gas formation.
From these experiments I can draw no other conclusion than
that the fermentation produced by the micro-organisms in ques-
tion is not accompanied by development of carbonic acid. This
process, writes Fliigge (Lit. 2, p. 483), which wholly foils to evolve
gases, does not meet the requirements of the ordinary definition
of fermentation, andean consequently not be considered as such.
The fermentation ceased in all cases which I have thus far
examined, when the substratum showed 0.75 per cent, of acid.
In the mouth, however, the fermentation can proceed without
interruption, since the acid formed is either washed away or
combines with the lime of the teeth and tartar.
As early as 1857, Pasteur- showed that the transformation of
sugar into lactic acid depended upon the presence of a species
of micro-organism.
The name of Bacillus acidi lactici (lactic acid bacterium) has
been given to a bacillus, first cultivated by Hueppe,-^ from sour
milk. Although very many difl'erent bacteria are known which
possess the power of converting carbohydrates into lactic acid,
it is thought that Hueppe's bacterium should be designated as
the lactic acid bacterium, since it is " by far the most frequent
cause of spontaneous lactic acid fermentation.'"
This bacillus forms short, plump rods, from 1-1. 7/^ long and
0.3-0.4// thick; it is immotile, forms spores. Below 10° C.
VITAL MANIFESTA TIONS OF BA CTERIA 2 1
velopment of bacteria and an acid reaction. 'No bubbles of gas
were seen to be ascending through the solution, or to have
accumulated upon its surface, as is frequently the case in such
cultures. Hereupon the end of the escape-tube was made to
dip into lime-water, in which the smallest quantity of CO^ escap-
ing from the flask would be readily detected by the cloudiness
occasioned by the formation of the carbonate of lime, but after
twelve hours no cloudiness had appeared. I then heated the
flask, in order to drive out any carbonic acid possibly formed
the lime-water, however, still remained clear. I repeated this
experiment with an apparatus for collecting the gas over mer-
cury. In a culture in which 1.75 grams of lactic acid were pro-
duced, only one little bubble of gas was collected, which might
as well have been caused by an imperceptible rise in the temper-
ature of the incubator as by actual gas formation.
From these experiments I can draw no other conclusion than
that the fermentation produced by the micro-organisms in ques-
tion is not accompanied by development of carbonic acid. This
process, writes Fliigge (Lit. 2, p. 483), which wholly foils to evolve
gases, does not meet the requirements of the ordinary definition
of fermentation, andean consequently not be considered as such.
The fermentation ceased in all cases which I have thus far
examined, when the substratum showed 0.75 per cent, of acid.
In the mouth, however, the fermentation can proceed without
interruption, since the acid formed is either washed away or
combines with the lime of the teeth and tartar.
As early as 1857, Pasteur- showed that the transformation of
sugar into lactic acid depended upon the presence of a species
of micro-organism.
The name of Bacillus acidi lactici (lactic acid bacterium) has
been given to a bacillus, first cultivated by Hueppe,-^ from sour
milk. Although very many difl'erent bacteria are known which
possess the power of converting carbohydrates into lactic acid,
it is thought that Hueppe's bacterium should be designated as
the lactic acid bacterium, since it is " by far the most frequent
cause of spontaneous lactic acid fermentation.'"
This bacillus forms short, plump rods, from 1-1. 7/^ long and
0.3-0.4// thick; it is immotile, forms spores. Below 10° C.
