The =trapezius= is much thicker and broader than in the horse, and is
undivided. It arises on the ligamentum nuchæ and supraspinous ligament,
from the atlas to the twelfth thoracic vertebra.
The =omo-transversarius= is a muscle (not present in the horse) which
arises on the wing of the atlas, and, inconstantly, the transverse
process of the second cervical vertebra, and is inserted into the
scapular spine and fascia.
The =rhomboideus= is clearly divided into cervical and dorsal portions,
the latter extending further than in the horse.
The =latissimus dorsi= has a broad tendon of origin, which blends with
the lumbo-dorsal fascia; it is also attached to the eleventh and twelfth
ribs, the fascia over the external intercostal and oblique abdominal
muscles, and by a tendinous slip to the deep pectoral muscle.
The =mastoido-humeralis= has two distinct parts. The dorsal division (M.
cleido-occipitalis) arises on the occipital bone and the ligamentum
nuchæ. The ventral part (M. cleido-mastoideus) is smaller and arises by
a round tendon on the mastoid process and the rectus capitis anterior
major, and by a thin tendon on the mandible. At the shoulder a small
muscle which arises on the first rib blends with the deep face of the
mastoido-humeralis.[75]
The =superficial pectoral= muscle does not present any striking
difference.
The =deep pectoral= arises as far forward as the second rib and is
undivided. However, the scapular portion may be considered to be
represented by a small branch extending over the lower part of the
supraspinatus. A tendon is detached from the dorsal edge, which blends
with the latissimus dorsi and coraco-brachialis.
The =serratus magnus= is clearly divided into cervical and thoracic
portions. The former is large and extends from the third (or second)
cervical vertebra to the fifth rib, being overlapped behind by the
thoracic part. The thoracic part is relatively thin and is covered by a
very strong aponeurosis; it is attached to the fourth to the ninth ribs
by six digitations, and is inserted by a flat tendon into the inner face
of the dorsal angle of the scapula.