eria.

~Ropy or slimy milk.~ The viscosity of milk is often markedly increased
over that which it normally possesses. The intensity of this abnormal
condition may vary much; in some cases the milk becoming viscous or
slimy; in others stringing out into long threads, several feet in
length, as in Fig. 17. Two sets of conditions are responsible for these
ropy or slimy milks. The most common is where the milk is clotted or
stringy when drawn, as in some forms of garget. This is generally due to
the presence of viscid pus, and is often accompanied by a bloody
discharge, such a condition representing an inflamed state of the udder.
Ropiness of this character is not usually communicable from one lot of
milk to another.

[Illustration: FIG. 17. Ropy milk.]

The communicable form of ropy milk only appears after the milk has been
drawn from the udder for a day or so, and is caused by the development
of various species of bacteria which find their way into the milk after
it is drawn. These defects are liable to occur at any season of the
year. Their presence in a dairy is a source of much trouble, as the
unsightly appearance of the milk precludes its use as food, although
there is no evidence that these ropy fermentations are dangerous to
health.

There are undoubtedly a number of different species of bacteria that are
capable of producing these viscid changes,[59] but it is quite probable
that they are not of equal importance in infecting milk under natural
conditions.

In the majority of cases studied in this country,[60] the causal
organism seems to be _B. lactis viscosus_, a form first found by Adametz
in surface waters.[61] This organism possesses the property of
developing at low temperatures (45 deg.-50 deg. F.), and consequently it
is often able in winter to supplant the lactic-acid forms. Ward has found
this germ repeatedly in water tanks where milk cans are cooled; and
under these conditions it is easy to see how infection of the milk might
occur. Marshall[62] reports an outbreak which he traced to an external
infection of the udder; in another case, the slime-forming organism was
abundant in the barn dust. A defect of this character is often
perpetuated in a dairy for some time, and may therefore become
exceedingly troublesome. In one instance in the writer's experience, a
milk dealer lost over $150 a month for several months from ropy cream.
Failure to properly sterilize cans, and particularly strainer cloths, i