SECRETION AND CONTAMINATION OF MILK. 15 
sugar into lactic acid and the milk becomes sour, other kinds 
produce a ropiness of the milk without souring it, and other 
forms produce gas in the milk; when made into cheese the curd 
from such milk becomes filled with gas holes. 
27. Varieties of Bacteria in Milk. 
The following are some of the more common conditions 
produced in milk by bacterial growth: 
Sour milk; gassy milk; bitter milk; slimy milk; soapy 
milk, which comes from a germ found on straw in the stable, 
producing a soapy taste and frothing of the milk; alcoholic 
fermentation; red milk; blue milk (not skimmed) ; green milk, 
etc. A bacillus known as coli communis which is present in im- 
mense numbers in the colon or larger intestine, finds its way 
from the manure into the milk and causes a large proportion 
of the gassy curds that our cheese makers have to deal with. 
This germ has been found to exist in the udder for a long time. 
It finds its way through the opening in the teat, gets a lodge- 
ment and remains there, to grow and contaminate the milk, 
until accidentally dislodged and carried out with the milk. 
Rusty spots in cheese are caused by bacillus rudensis (222). 
28. How Milk is Infected. 
When the milk is drawn from the udder, bacteria floating 
separately or clinging to particles of dust in the air fall into it. 
It will readily be seen that if the stable is clesed tight and hay 
has been fed just before milking, a great deal of bacteria-laden 
dust will be stirred up and fall into the milk pail. If the cow 
lies down in the manure, or other filth, at milking time, the dust 
from this is stirred up and falls into the milk. Warm milk is 
a good medium for the germs to grow in, and they multiply 
very rapidly therein. If the milk is cooled the growth of the 
bacteria is checked for the time, but on warming up the milk 
again they will grow and multiply rapidly. 
29. The Wisconsin Curd Test. 
While associated in dairy work with Drs. Babcock and 
Russell at the Wisconsin Experiment Station, the author brought 
out what is known as the Wisconsin Curd Test for the detection 
of injurious milk fermentations. The apparatus ccnsists of pint, 
