ANATOMY OF THE HORSE. 
187 
Attachment .—On the inner side, to a white tendinous line, 
and through the medium of that, to its fellow of the opposite side; 
also to the four first bones of the sternum: on the outer side, to 
the anterior part of the body of the humerus, and to the faschia 
covering the arm. 
Relations .—Superiorly, it is connected with the major and 
minor pectoral muscles ; externally it is covered by the skin; in¬ 
ternally, opposed to the front of the elbow joint; anteriorly, to 
the levator humeri. 
Direction .—Transverse; incurvating downwards. 
Structure . —Inner attachments, as well as fleshy; outer, 
wholly aponeurotic : intermediate part, fleshy. 
Action . —To adduct the arm, and keep it close to the chest 
during its flexion and extension: this muscle has, probably, more 
to do in enabling the arm to support weight than to give it motion. 
pectoralis magnus .— Sterno-trochineus. 
Situation .—Infero-lateral part of the thorax. 
Figure .—Trapezoid; flattened and thick in substance. 
Attachment .—Inwardly, to the 4th, 5th and 6th pieces of 
the sternum, and to the cartilages connecting them; also to the 
cusiform cartilage, where, through the intervention of a white 
tendinous line, it becomes united with its fellow; still more pos¬ 
teriorly, to the aponeurosis of the external oblique muscle, and 
the cartilages of the false ribs: outwardly, it is attached to the 
lesser tubercle of the humerus and the inner part of the lower 
end of the scapula. 
Relations .—Externally, with the panniculus and triceps mus¬ 
cles ; internally, with the aponeurosis of the external oblique, 
the serratus magnus, and the ribs : inferiorly, with its fellow, and 
in part concealed by the next muscle. 
Direction .—Longitudinal: inclining upwards. 
Structure.—' Fleshy : only that its anterior end is in part apo¬ 
neurotic. 
Action .— To draw the head of the humerus, and along with 
it the lower end of the scapula, backwards, throwing the latter 
more into the upright position. 
PECTORALIS PARVUS. 
Situation .— Below the former muscle. 
Attachment .— Inwardly, to the side of the anterior half of the 
sternum, and to the cartilages of the first four ribs: outwardly, 
to the faschia covering the muscles in front of the scapula and 
shoulder-joint, extending nearly as high up as the place of origin 
of the antea-spinatus. 
