ABNORMAL MILK. 57 
fully, be mistaken for colostrum. Bloody milk produced by an 
inflamed udder, may be distinguished by noticing small blood 
particles, which will settle to the bottom, and can be noticed if 
the sample is placed in a glass test-tube. Bloody milk caused by 
bacterial growth does not show the blood at the bottom, but 
instead, previous to stirring the milk or cream, it appears on 
the surface in small red dots. The red golor which commonly 
occurs in milk is due chiefly to a species of germ called Micro- 
coccus prodigiosus. Colostrum will show reddish cream on the 
surface, but no blood-like material will separate out. 
Blue Milk.—Blue milk is quite commonly found. Formerly 
it was thought that this color was due to the condition of the 
casein in the milk, but since more has been discovered in regard 
to the effect of germ life upon conditions and properties of milk, 
it has been proved that blue milk is caused by bacteria* (Bacil- 
lus cyanogenus). This particular germ produces the blue color 
in the milk only when the milk has an acid reaction. When 
sterile milk is inoculated with this particular germ, the blue 
color is not produced, but by the addition of a little acid, or by 
inoculating the milk with the bacteria that produce lactic acid, 
the blue color is produced. This seems to be one of the instances 
of symbiotic action of bacteria in milk. There are probably 
other causes, but they are not known. This germ, according 
to Aikman, is killed by heating the milk to about 176° F. The 
germ ceases to work as soon as milk is coagulated. 
Yellow Milk.—According to Aikman,* yellow milk is caused 
chiefly by one species of bacteria, named Bacillus synxanthus. 
This micro-organism belongs to the group of ferments that act 
upon the fat of milk. There are different shades of yellow 
produced in milk, caused by different species of bacteria, but 
the above-mentioned one is considered to be the principal cause. 
Some produce a brilliant yellow color, while other species first 
curdle the casein, and then digest or dissolve it into a yellow 
or amber-colored liquid. 
*(C, M. Aikman, in ‘‘ Milk, Its Nature and Composition.” 
