386 
Micro-organisms and their Action 
drawn from the cow is already infested with the ferment which 
later on leads to its becoming slimy, or that the milk is infected 
at a stage after it has left the cow. The first assumption has 
not yet been disproved, no experiments having been made to 
show that milk which has been drawn from the cow under 
proper precautions will never get ropy. The second assumption 
however has been fully proved in practice, as well as by scien- 
tific experiments. Undoubtedly sound milk brought in contact 
with, or even kept in the same room with, ropy milk, soon 
becomes ropy also. When ropy milk is subjected to micro- 
scopic examination, it invariably exhibits small cells of very 
high refractive power ; these cells are either single or united in 
bead-like chains. 
If sterilized milk be inoculated with ropy milk and kept at a 
suitable temperature, it will be observed that no cream rises to 
the top, and that the milk gets ropy within twenty-four hours ; it 
is then slightly acid. After forty-eight hours have elapsed, the 
milk is of such a consistency that it will not flow out of the 
vessel containing it, even if the latter be turned upside down. 
If in place of milk whey be infected, and also if a solution of 
milk-sugar containing small quantities of nitrogenous bodies, 
and certain mineral compounds be operated upon, the effect is 
the same, although perhaps not quite so marked. Solutions of 
casein or albumen, on the other hand, are not affected by the 
inoculation of ropy milk, showing that it is not the nitrogenous 
compounds, but the milk-sugar which is attacked. Correspond- 
ing with the advance of the fermentation, the quantity of milk- 
sugar is more and more diminished. By examination with 
the microscope a micrococcus has been found to be present in 
slimy milk. 
The most suitable temperature for this development is between 
86° and 104° Fahr. With the rise of temperature, the energy 
of the micrococcus is diminished, and at 140° Fahr. it is alto- 
gether destroyed. If ropy milk, however, be dried at relatively 
low temperatures, and the dry mass exposed to a temperature of 
212° Fahr. for several minutes, it does not lose its irtfective 
character. Freezing prevents the development of the micro- 
coccus and the exercise of its effect, but it does not kill it. 
There exists another micro-organism generally causing slimy 
fermentation and very commonly found upon potatoes, which 
is also able to act upon milk. It is a micro-organism of a 
different form belonging to the class of bacilli, and its action 
on milk is very different from that of the micrococcus pre- 
viously described. 
The bacillus when introduced into sterilized milk first causes 
precipitation, and afterwards dissolution of the casein, which latter 
