reported as
well as gas-producing[13] forms allied to the colon bacillus. Such
findings are, however, due in all probability to accidental invasion.
Most investigators report the absence of the distinctively lactic-acid
group of organisms.[14]

~Origin of bacteria in udder.~ There is no question but that many of the
types of bacteria found in the udder gain access from the outside. Those
belonging to the spore-bearing, digesting and intestinal types have such
a favorable opportunity for introduction from outside and are so
unlikely to have come directly from the body of the animal, that the
external source of infection is much more probable. Whether this
explanation answers the origin of the cocci that are so generally found
in the upper portion of the udder is questionable. The statement is
ordinarily made that the inner tissues of healthy organs are
bacteria-free, but the studies of Ford[15] seem to indicate that 70 per
cent. of such organs, removed under aseptic conditions from guinea pigs,
rabbits, dogs and cats contained living organisms. Others have reported
similar results in which cocci have been found[16] very similar to those
occurring in the udder. These findings increase the probability that the
origin of this type is from the blood. The persistence of certain
species in the udder for months as noted by Ward indicates possibility
of growth of some forms at least. Stocking[17] has shown where cows are
not milked clean that the germ content of succeeding milkings is greatly
increased.

~Artificial introduction of bacteria into udder.~ If bacteria are capable
of actually developing in the udder proper, it ought to be possible to
easily demonstrate this by the artificial introduction of cultures. In a
number of cases[18] such experiments have been made with various
saprophytic forms, such as _B. prodigiosus_, lactic acid bacilli and
others. In no case has it appeared evident that actual growth has
occurred, although the introduced organism has been demonstrated in
diminishing numbers for 5-6 days. Even the common lactic acid germ and a
yellow liquefying coccus isolated from the fore milk failed to persist
for more than a few days when thus artificially introduced. This failure
to colonize is indeed curious and needs explanation. Is it due to
unsuitable environmental conditions or attributable to the germicidal
influence of the milk?

Various body fluids are known to possess the property of destroying
bacter