THE HUMERUS
The humerus is almost
entirely clothed by the muscles which surround it, and the only parts of this
bone which are strictly subcutaneous are small portions of the internal and
external condyles. In addition to these, the tuberosities and a part of the
head of the bone can be felt under the skin and muscles by which they are
covered. Of these the greater tuberosity forms the most prominent bony point of
the shoulder, extendinll: beyond the acromion process and covered by the
Deltoid muscle. It influences materially the surface form of the shoulder. It
is best felt while the arm is lying loosely by the side; if the arm be raised,
it recedes from under the finger. The lesser tuberosity, directed forward and
inward, is to be felt to the inner side of the greater tuberosity, just below
the acromio-clavicular joint. Between the two tuberosities lies the bicipital
groove. This can be defined by placing the finger and making firm pressure just
internal to the greater tuberosity; then, by rotating the humerus, the groove
will be felt to pass under the finzer as the bone is rotated. With the arm
abducted from the side, by pressing deeply in the axilla the lower part of the
head of the bone .is to be felt. On each side of' the elbow-joint, and just
above it, the internal and external condyles of the bone are to be felt. Of
these the internal is the more prominent, but the ridge passing upward from it,
the internal condyloid ridge, is much less marked than the external, and, as a
rule, is not to be felt. Occasionally, however, we find along this border the hook-shaped
process mentioned above. The external condyle is most plainly
to be seen during semiflexion of the forearm, and its position is indicated by
a depression between the attachment of the adjacent muscles. From it is to be
felt a strong bony ridge running up the outer border of the shaft of the bone.
This is the external supracondylar ridge; it is conc-ave forward, and
corresponds with the curved direction of the lower extremity of the humerus.
