al of whey.]

More convenient types of this test than the improvised apparatus just
alluded to have been devised by different dairy manufacturers.
Generally, they consist of a special bottle having a full-sized top,
thus permitting the easy removal of the curd. The one shown in Fig. 18
is provided with a sieve of such construction that the bottles will
drain thoroughly if inclined in an inverted position.

~Interpretation of results of test.~ The curd from a good milk has a firm,
solid texture, and should contain at most only a few small pin holes. It
may have some large, irregular, "mechanical" holes where the curd
particles have failed to cement, as is seen in Fig. 19. If gas-producing
bacteria are very prevalent in the milk, the conditions under which the
test is made cause such a rapid growth of the same that the evidence of
the abnormal fermentation may be readily seen in the spongy texture of
the curd (Fig. 20). If the undesirable organisms are not very abundant
and the conditions not especially suited to their growth, the "pin
holes" will be less frequent.

[Illustration: FIG. 19. Curd from a good milk. The large irregular holes
are mechanical.]

Sometimes the curds show no evidence of gas, but their abnormal
condition can be recognized by the "mushy" texture and the presence of
"off" flavors that are rendered more apparent by keeping them in closed
bottles. This condition is abnormal and is apt to produce quite as
serious results as if gas was formed.

~Overcoming taints by use of starters.~ Another method of combatting
abnormal fermentations that is often fruitful, is that which rests upon
the inability of one kind of bacteria to grow in the same medium in
competition with certain other species.

Some of the undesirable taints in factories can be controlled in large
part by the introduction of starters made from certain organisms that
are able to obtain the ascendency over the taint-producing germ. Such a
method is commonly followed when a lactic ferment, either a commercial
pure culture, or a home-made starter, is added to milk to overcome the
effect of gas-generating bacteria.

[Illustration: FIG. 20. Curd from a badly tainted milk. Large ragged
holes are mechanical; numerous small holes due to gas. This curd was a
"floater."]

A similar illustration is seen in the case of the "lange wei" (slimy
whey), that is used in the manufacture of Edam cheese to control the
character of the fermentation of the