housandth of its
original number by using care in milking. He reports a series of
experiments covering two years in which milk was secured that averaged
less than 10,000 bacteria per cc., while that secured under ordinary
conditions averaged over 500,000.

[Illustration: FIG. 12. Bacterial content of milk handled in ordinary
way. Each spot represents a colony growing on gelatin plate. Compare
with Fig. 13, where same quantity of milk is used in making culture.
Over 15,000 bacteria per cc. in this milk.]

Fig. 13 gives an illustration as to what care in milking will do in the
way of eliminating bacteria. Fig. 12 shows a gelatin plate seeded with
the same quantity of milk that was used in making the culture indicated
by Fig. 13. The first plate was inoculated with milk drawn under good
conditions, the germ content of which was found to be 15,500 bacteria
per cc., while the sample secured under as nearly aseptic conditions as
possible (Fig. 13) contained only 330 organisms in the same volume.

[Illustration: FIG. 13. Bacterial content of milk drawn with care.
Diminished germ content is shown by smaller number of colonies (330
bacteria per cc.). Compare this culture with that shown in Fig. 12.]

~"Sanitary" or "certified" milk.~ Within recent years there has been more
or less generally introduced into many cities, the custom of supplying
high grade milk that has been handled in a way so as to diminish its
germ content as much as possible. Milk of this character is frequently
known as "sanitary," "hygienic" or "certified," the last term being used
in connection with a certification from veterinary authorities or boards
of health as to the freedom of animals from contagious disease.
Frequently a numerical bacterial standard is exacted as a pre-requisite
to the recommendation of the board of examining physicians. Thus, the
Pediatric Society of Philadelphia requires all children's milk that
receives its recommendation to have not more than 10,000 bacteria per
cc. Such a standard has its value in the scrupulous cleanliness that
must prevail in order to secure these results. This in itself is
practically a guarantee of the absence of those bacteria liable to
produce trouble in children. The number of organisms found in such milks
is surprisingly low when compared with ordinary milk. Naturally, there
is considerable fluctuation from day to day, and occasionally the germ
content is increased to a high figure without any apparent