110 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
toms of constitutional disturbance. There is then more 
or less extensive and painful swelling of the affected 
quarter which begins at the teats and extends upward. 
The milk secretion is somewhat reduced in quantity in 
the beginning of the disease, but is otherwise unchanged. 
Later, the secretion from the affected quarter is dimin- 
ished ; the fat is decreased and the milk has a pale, watery 
appearance. The inflammation may extend into the 
gland tissue, in which case the milk will undergo the same 
changes as in parenchymatous mastitis. 
Harmful Properties of Mastitis Milk.—In mastitis 
the secretion from the udder nearly always contains bac- 
teria which may be harmful to man. In the catarrhal 
form streptococci are usually present, sometimes staphy- 
lococci or the Bacillus pyogenes. In the parenchymatous 
form bacteria of the colon group are usually present, 
sometimes bacilli of the paratyphus or paracolon group, 
the enteriditis bacillus, or staphylococci. In catarrhal 
mastitis the bacteria may be present when the milk is of 
normal appearance and before clinical symptoms appear 
and also after the clinical symptoms have subsided and 
the milk has again become normal in appearance. Bac- 
teria not only occur in the secretion from the affected 
quarter but they may also be present in the milk from the 
other quarters. The skin of the teats and udder is con- 
taminated by the secretion from the diseased quarter and 
some of this infected material can easily fall into the milk 
pail during the drawing of milk from the other quarters. 
Secondary infection of the milk is also likely to occur 
when the secretion from the diseased quarter is milked 
onto the floor, as is frequently done. The mastitis bac- 
teria find an excellent culture media in milk and rapidly 
multiply when the milk is kept at room temperature. 
