thorax and converges to insert on the
ventral side of the humerus on the pectoral surface.

~_M. supracoracoideus_~, Fig. 1. The origin is from the dorsal portion of
the keel and medial portion of the sternum, and is bordered ventrally by
the origin of M. pectoralis thoracica, and laterally by _M.
coracobrachialis posterior_. The origin is also from the manubrium and
the anterolateral portion of the proximal half of the coracoid and to a
slight extent from the sterno-coraco-clavicular membrane adjacent to the
manubrium. This large pinnate muscle converges, passes through the
foramen triosseum, and inserts by a tendon on the external tuberosity of
the humerus, immediately proximal to the insertion of _M. pectoralis
thoracica_.

~_M. coracobrachialis posterior_~, Figs. 1 and 3. The origin is from the
dorsolateral half of the coracoid, anterolateral portion of the sternum
(where the area of origin is bordered medially by _M. supracoracoideus_,
posteriorly by _M. pectoralis thoracica_, and laterally by _M.
sternocoracoideus_), and also to a slight extent from the area of
attachment of the thoracic ribs to the sternum. The muscle fibers
converge along the lateral edge of the coracoid and insert on the median
crest of the humerus immediately proximal to the pneumatic foramen. In
passing from the origin on the sternum to the insertion on the humerus,
the belly of the muscle bridges the angle formed by the costal process
of the sternum and the coracoid.

~_M. sternocoracoideus_~, Figs. 2 and 3. The origin is from the entire
external surface of the costal process of the sternum, and to a small
extent from the extreme proximal ends of the thoracic ribs where they
articulate with the costal process. The muscle inserts on a triangular
area on the dorsomedial surface of the coracoid. Like _M.
coracobrachialis posterior_, this muscle bridges the angle formed by the
costal process and the coracoid.

~_M. subcoracoideus_~ (ventral head), Figs. 2 and 3. The origin is from
the dorsomedial edge of the coracoid at its extreme proximal end, and to
a slight extent from the adjacent portion of the manubrium. The origin
is medial to the insertion of _M. sternocoracoideus_. The ventral head
passes anterodorsally along the medial edge of the coracoid and joins
the dorsal head (not here described). The combined muscle then inserts
by a tendon onto the internal tuberosity of the humerus.

~_M. costi-sternalis_~, Figs. 1, 2, and 3. The origin