t.

Although the evidence that milk may not infrequently serve as an agent
in spreading disease is conclusive enough to satisfactorily prove the
proposition, yet it should be borne in mind that the organism of any
specific disease in question has rarely ever been found. The reasons for
this are quite the same as those that govern the situation in the case
of polluted waters, except that the difficulties of the problem are much
greater in the case of milk than with water. The inability to readily
separate the typhoid germ, for instance, from the colon bacillus, an
organism frequently found in milk, presents technical difficulties not
easily overcome. The most potent reason of failure to find disease
bacteria is the fact that infection in any case must occur sometime
previous to the appearance of the outbreak. Not only is there the usual
period of incubation, but it rarely happens that an outbreak is
investigated until a number of cases have occurred. In this interim the
original cause of infection may have ceased to be operative.

~Typhoid fever.~ With reference to the diseases likely to to be
disseminated through the medium of milk, infected after being drawn from
the animal, typhoid fever is the most important. The reason for this is
due (1) to the wide spread distribution of the disease; (2) to the fact
that the typhoid bacillus is one that is capable of withstanding
considerable amounts of acid, and consequently finds even in raw milk
containing the normal lactic acid bacteria conditions favorable for its
growth.[113] Ability to grow under these conditions can be shown not
only experimentally, but there is abundant clinical evidence that even a
slight infection often causes extensive outbreaks, as in the Stamford,
Conn., outbreak in 1895 where 386 cases developed in a few weeks, 97 per
cent. of which occurred on the route of one milk-man. In this case the
milk cans were thoroughly and properly cleaned, but were rinsed out with
_cold_ water from a shallow well that was found to be polluted.

The most common mode of pollution of milk with typhoid organisms is
where the milk utensils are infected in one way or another.[114] Second
in importance is the carrying of infection by persons serving in the
dual capacity of nurse and dairy attendant.

~Cholera.~ This germ does not find milk so favorable a nutrient medium as
the typhoid organism, because it is much more sensitive toward the
action of acids. Kitasato[115] found