tock. Dairy
cattle are, however, not more susceptible, but the closer
environment in which milch cattle are kept, and the fact that there
has been greater activity in the matter of introducing improved
strains, accounts for the larger percentage of affected animals.

It has been a disputed question for some years whether the organisms
producing bovine and human tuberculosis are identical or from the
practical standpoint, whether the bovine type of disease is
transmitted under natural conditions to man. The bacteriologist can
readily detect differences in appearance, in growth of cultures, and
in disease-producing properties between the two strains. Of the two,
the bovine is much the more virulent when inoculated into
experimental animals. In a considerable number of cases, record of
accidental infection from cattle to man has been observed. These
have occurred in persons making postmortem examination on
tuberculous animals, and the tubercular nature of the wound proven
by excision and inoculation.

More recently, since the agitation by Robert Koch of Germany, a
number of scientific commissions have studied particularly the
problem of transmission. It is now estimated that perhaps seven per
cent of the tuberculosis in man is of bovine origin. This is almost
wholly confined to children. The portions of the body that become
diseased, when the infection has resulted from the use of milk, are
the glands of the neck and of the abdomen.

=Manner of infection in man.= In the main, the source of the malady
may be traced either to air infection or to the food, if one
disregards the comparatively small number of cases of wound
infection. Air is frequently a medium by which the germ is
transferred from one person to another. The sputum is exceedingly
rich in tubercle bacilli and since this material is carelessly
distributed by tubercular people, the air of the cities, villages
and public buildings will frequently contain tubercle organisms.
Some of the organisms in the air find their way into the lungs,
there to develop and produce consumption. The organisms in the air
may be deposited in the nasal passages and throat, and ultimately
find their way into the tissues of the body by penetrating the walls
of the throat or of the intestine. It is probable that the tubercle
bacilli thus introduced may find their way to the lungs and there
develop without leaving any trace of their path.

Food may also possibly serve as a medium of