ANATOMY OF THE HORSE: 
5 42 
Structure .—Even this large head itself may be dissected into 
two portions (to which Bourgelat and Girard have given dis¬ 
tinct names): one is long, thm, and flattened, and aponeurotic 
at its attachments, but fleshy in its middle, and lies along the 
postero-internal border of the other, which constitutes the chief 
bulk of the entire muscle. 
The scapular att \chments are fleshy upon the outer side, ten¬ 
dinous upon the inner. The surfaces are in places aponeurotic. 
The belly or middle part is fleshy, with the exception of a thick 
tendinous intersection, which, together with the aponeurosis, 
ends in a broad, thick, flattened tendon, that is implanted into 
the olecranon. 
caput medium. — Humero-olecranius Externus. 
Situation. —Infero-external part of the shoulder. 
Form .— Oblong- flattened. 
Attachment .—Superiorly, from the outer side of the neck, and 
from the ridge extending from the outer tubercle upon the body 
of the humerus: inferiorly, to the postero-outer parts of the 
olecranon. 
Direction .—From above, downwards; and from before back¬ 
wards. 
Relations .—Externally, with the postea-spinatus, teres minor, 
and faschia and skin; internally, with the humeralis externus 
and outer condyle of the humerus: anteriorly, with the faschia 
and skin; posteriorly, with the caput magnum. 
Structure .—Superior attachment, both fleshy and tendinous. 
Middle part, fleshy. Inferior attachment, fleshy and tendinous, 
and inseparably united in one common tendon with the caput 
magnum. 
caput parvum. — Humero olecranius Internus . 
Situation .—Infero-internal part of the shoulder. 
Form .—Long and slender; and flattened. 
Attachment. —Superiorly, to the inner side of the body of the 
humerus, just above its middle: inferiorly, to the inner part of 
the apex of the olecranon. 
Relations. —Externally, with the caput magnum, teres major, 
and latissimus dorsi; internally, with the humerus. 
Structure. —Superior attachments, tendinous and fleshy; sur¬ 
faces, slightly aponeurotic; inferior attachment by a thin flattened 
tendon. 
Action of the Three Heads (considered as a single muscle,) - 
To extend the arm. 
