( 679 ) 
In fig. 6 we see the rate of development of fat-splitting and 
that of the lactic acid ferments in milk kept under circumstances 
of temperature and oxygen pressure, such as is usually done in 
practice. (On the abseis 100 million bacteria are represented by 
one em, on the ordinate 24 hours by 1 em.). For this a 1 liter 
flask of 800 ce. of good clean milk was kept in a cellar at + 10°; 
after every 24 hours the number of lactic acid ferments and that of 
the fat-splitting microbes was determined. 
The bacterial ciphers used to construct the graphics, show that the 
proportion of the lactic acid ferments to the fat-splitting bacteria 
/ 
in the milk at the beginning was */,; that same day after 8 hours 
ands vibiees), ollewime-\ days, respectively) *f95 llen Ul °° 
Loof, 106/. During the first five days the number of fat-splitting 
microbes increased, but less rapidly than that of the lactic acid fer- 
ments; thereupon a relatively rapid destruction takes place at an 
acid degree of = 85. The regularly increasing rate of acid appears 
to do little harm to the lipase producing bacteria, so sensitive to 
acidity, although these at a direct inoculation into acid milk, titrating 
au ec.,~/,,, N- per, 100..ce.,1 no more. grow ;. hence it is evident 
that they adapt themselves to the acid degree. To the fat-splitting 
species in this milk belonged : /lworescents, mecrococct and the group 
of B. Lipolyticum, described page 674. 
The bacteria of putrefaction happening to get into the milk with 
the faeces of the cows or from the air of the stable, contain for the 
greater part lipolytic enzymes as for instance the aérobic species 
B. vulgare, B. prodigiosum, B. jluorescens liquefaciens, B. pyocya- 
neum and the anaërobie Bacillus putrijicus, which last species is 
often met with in pasteurised milk. 
The changes provoked in milk by the fat-splitting microbes are, 
excepting those caused by the lipolytic influence of the microbes, 
more particularly to be aseribed to their peptonising action. To 
milk they give a cheesy or soapy smell and often a bitter taste ; they 
cause rapid creaming and render the suspended fat rancid as also 
the butter made from it. 
Hence we must consider these bacteria as the most dreaded enemies 
of the dairy- and fat industry. 
SUMMARY. 
1. The fat-splitting power of aérobic as well as of anaérobic 
micro-organisms and their power of denitrifying with fat, may in a 
simple way be determined by means of fatted test-tubes. 
44* 
