e stage where it plays its most conspicuous part.
Every part of the system is more or less involved, every vital operation
more or less deranged; especially is the _nutritive_ function vitiated
and imperfect. The circulation is also involved in the general morbid
condition. Tubercles, which constitute a marked feature of the disease,
are composed of unorganized matter, deposited from the blood in the
tissue of the lungs. They are small globules of a yellow, opaque,
friable substance, of about the consistency of cheese. After their
deposition, they are increased in size by the accretion of fresh matter
of the same kind. They are characteristic of all forms of scrofulous
disease.

The most plausible theory in regard to them is, that they are the result
of imperfect nutrition. Such a substance cannot be produced in the blood
when this fluid is perfectly formed. It is an unorganized particle of
matter, resulting from the imperfect elaboration of the products of
digestion, which is not, therefore, properly fitted for assimilation
with the tissues. The system being unable to appropriate it, and
powerless to cast in off through the excretory channels, deposits it in
the lungs or other parts of the body. There it remains as a foreign
substance, like a splinter or thorn in the flesh, until ejected by
suppuration and sloughing of the surrounding parts. It might be supposed
by some that when the offending matter was thus eliminated from the
lungs, they would heal and the patient recover; but, unfortunately, the
deposition of tubercular matter does no cease. Owing to the morbid
action of the vital forces, it is formed and deposited as fast or
faster than it can be thrown off by expectoration. Hence arises the
remarkable fatality of pulmonary consumption.

CAUSES. The causes of consumption are numerous and varied, but may all
be classed under two heads, viz: _Constitutional_, or _predisposing_,
and _local_, or _exciting_. Of just what tubercular matter consists, is
still a subject of controversy, but that its existence depends upon
certain conditions, either _congenital_ or _acquired_, is generally
conceded; and one of these conditions is impaired vitality.
Constitutional predisposition must first give rise to conditions which
will admit of the formation of tubercular matter, before any cause
whatever can occasion its local deposition. It must modify the vitality
of the whole system, when other causes may determine in the system th