the wall of the bowel into the lacteals, along
which they pass to the mesenteric glands where they become arrested and
give rise to tuberculous disease.

#Relationship of Tuberculosis to Trauma.#--Any tissue whose vitality has
been lowered by injury or disease furnishes a favourable nidus for the
lodgment and growth of tubercle bacilli. The injury or disease, however,
is to be looked upon as determining the _localisation_ of the
tuberculous lesion rather than as an essential factor in its causation.
In a person, for example, in whose blood tubercle bacilli are
circulating and reaching every tissue and organ of the body, the
occurrence of tuberculous disease in a particular part may be determined
by the depression of the tissues resulting from an injury of that part.
There can be no doubt that excessive movement and jarring of a limb
aggravates tuberculous disease of a joint; also that an injury may light
up a focus that has been long quiescent, but we do not agree with
those--Da Costa, for example--who maintain that injury may be a
determining cause of tuberculosis. The question is not one of mere
academic interest, but one that may raise important issues in the law
courts.

#Human and Bovine Tuberculosis.#--The frequency of the bovine bacillus
in the abdominal and in the glandular and osseous tuberculous lesions of
children would appear to justify the conclusion that the disease is
transmissible from the ox to the human subject, and that the milk of
tuberculous cows is probably a common vehicle of transmission.

#Changes in the Tissues following upon the successful Lodgment of
Tubercle Bacilli.#--The action of the bacilli on the tissues results in
the formation of granulation tissue comprising characteristic tissue
elements and with a marked tendency to undergo caseation.

The recognition of the characteristic elements, with or without
caseation, is usually sufficient evidence of the tuberculous nature of
any portion of tissue examined for diagnostic purposes. The recognition
of the bacillus itself by appropriate methods of staining makes the
diagnosis a certainty; but as it is by no means easy to identify the
organism in many forms of surgical tuberculosis, it may be necessary to
have recourse to experimental inoculation of susceptible animals such as
guinea-pigs.

The changes subsequent to the formation of tuberculous granulation
tissue are liable to many variations. It must always be borne in mind
that althou