444 
ACUTE INFLAMMATION OF THE UDDER. 
that the milk seldom remains pent up in the udder for any long time. 
Numerous experiments, in which pure cultures of particular bacteria have 
been injected into the galactophorous sinuses, show, however, that inflam¬ 
mation may start here. Ivitt even produced mastitis by painting the teat 
with a pure culture. 
Of late it has been much disputed whether inflammation of the udder 
can be caused by not milking the animal. Whilst this was formerly 
regarded as a frequent cause of mastitis, the general view nowadays is, 
that retention of the milk alone never produces disease of this description. 
It is clear that neither view is quite right. The retention of milk, as 
such, certainly does not produce mastitis, but it favours its production, 
because of the readiness with which decomposition and the growth 
of bacteria occur in the retained milk, and secondarily produce 
inflammation. 
This explains why mastitis is most common during hot weather; 
Strebel says most cases occur between March and September. Other 
factors may also be at work, such as the animal’s condition, the attention 
it receives, and the time during which the calf is with it; but this much 
is unquestionable, that warm weather favours decomposition of the milk, 
and the multiplication of bacteria in it. 
(3) Finally, infection through the blood stream appears possible 
(hematogenous mastitis), though it is probably very rare. 
It also seems possible that when the disease is widely spread, or con¬ 
ditions are favourable for the transmission of the specific microbe, 
mastitis may take an epizootic form; the infected material being easily 
cairied from animal to animal during milking. It is not astonishing, 
considering, the varying virulence of pathogenic microbes, that many 
different forms of udder infection occur, so that sometimes only slight 
inflation, sometimes severe inflammation, and sometimes .gangrene 
results. We divide the acute inflammatory processes in the udder into 
two groups, viz.:— 
A. Acute inflammations of the udder. 
(a) Phlegmonous mastitis. 
( b ) Catarrh of the udder. 
(c) Purulent inflammation of the udder. 
(d) Gangrenous inflammation of the udder. 
B. Chronic inflammations of the udder. 
(a) Infectious catarrhal mastitis. 
(b) Tuberculosis of the udder. 
(c) Actinomycosis of the udder. 
(d) Bothrvomycosis of the udder. 
These varying forms can be clinically differentiated, and yet in a 
geneial sense the classification is m harmony with the aetiology of the 
