r which the blacksmith's
arm is called upon to perform produces hypertrophy of its muscles. With
this condition, the pulse is hard and incompressible, and the line of
ascent in the sphygmographic tracing (Fig. 3) is higher than in health.

[Illustration: Fig. 3.]

DILATATION OF THE HEART is a condition which is closely allied to
hypertrophy of the heart, and which consists of an increase in the
capacity of the cavities of the heart, with diminished contractile
power. In simple dilatation, there is an increase in the capacities of
the cavities, without any marked change in the walls of the organ. It is
usually the result of some disease which has produced great muscular
prostration, and which has interfered materially with nutrition. More
frequently, however, dilatation is the result of valvular lesions, and
is associated with hypertrophy, there being an increase in the thickness
of the walls with a diminution of the contractile power. The hypertrophy
from valvular lesions goes on increasing until it reaches a certain
stage, when dilatation commences, the two conditions then being
associated.

ATROPHY of the heart is the opposite to hypertrophy, and signifies a
wasting away of the muscular substance, and a diminution in the
thickness of the walls of the heart. Its power is diminished in
proportion to the degree of atrophy.

FATTY DEGENERATION of the heart consists in the deposition of particles
of fat within the _sarcolemma_ (the sheath which invests the fibrils),
which are substituted for the proper muscular tissue. If the fatty
degeneration exists to any extent the muscular walls present a yellowish
color, and the heart is soft and flabby. This may be confined to one
ventricle, or it may affect the inner layer of fibres, the outer layer
remaining unchanged. Degeneration of the left ventricle occasions
feebleness of the pulse. Difficulty in breathing is one symptom of this
disease, especially when the right ventricle is affected. There is
pallor, feeble circulation, cold extremities, and frequently dropsy.
Fatty degeneration is more liable to occur in corpulent persons, and
between the ages of forty and fifty years.

ANGINA PECTORIS, also termed _neuralgia of the heart_, might be included
among the diseases of the nervous system, but as it is usually
associated with a derangement in the action of the heart, it may be
properly considered in this connection. The pain varies in intensity,
sometimes being very acute,