Where milk is delivered at the factory, we have as yet no standard
test of value. All the receiver can do is to see that it is in a
normal condition--neither sour nor tainted, nor containing bad odors.
For this purpose, the smell must mainly be relied on. Hence, healthy
and keen olfactories are a great aid here, as in some other cases. If
one catches the fumes when the can cover is first removed, or as the
milk runs into the weighing can, he is pretty sure to detect any very
positive bad odor. The eye, to one of experience, is almost certain to
detect any great variation. Even slight watering is seen by some from
the peculiarity of the reflection of light from the surface--especially
when in motion. Much water shows from the "thin" appearance of the
fluid. Where the smell or appearance are cause for suspicion, or there
is any other cause, a sample may be saved and such tests as are at
hand may be applied. The so-called lactometer will show whether the
specific gravity is below or above the normal standard. The cream gauge
will give the percent of cream at a given temperature. If, afterward,
a sample right from the herd, taken so as to know that it has not been
tampered with, shows better quality by these two tests, it is pretty
conclusive evidence that the milk from which the factory sample was
taken was not in a normal condition. If the herd has been subject to
no change of feed or conditions between the times of taking the two
samples, any jury would be safe in bringing in a verdict against the
defendant for watering, skimming, or otherwise tampering with his milk,
as the facts in evidence might indicate.