_a_, Mylo-hyoideus; _b_, digastricus; _c_, sterno-hyoideus; _c′_,
sterno-thyroideus; _d_, sterno-cephalicus; _e_, brachiocephalicus;
_f_, subscapularis; _g_, superficial pectoral; _h_, deep pectoral;
_i_, rectus abdominis; _k_, obliquus abdominis externus; _l_, long
head of triceps; _m_, internal head of triceps; _n_, biceps brachii;
_o_, brachialis; _1_, _1′_, _1″_, submaxillary lymph glands; _2_,
thyroid gland; _3_, external jugular vein. (Ellenberger-Baum, Anat.
d. Hundes.)
]
The =latissimus dorsi= is extensive, and has a fleshy attachment to the
last two ribs. Its lower edge blends near the shoulder with the
panniculus.
The =mastoido-humeralis= contains in front of the shoulder a fibrous
mass in which the clavicle is embedded. Anterior to this it separates
into two diverging portions. The =dorsal portion= (M. cleido-cervicalis)
is attached to the median raphé of the neck and to the occipital bone.
The =ventral portion= (M. cleido-mastoideus) is attached to the mastoid
process. The common mass posterior to the clavicle and the fibrous
intersection, which is attached to the humerus, is homologous with the
clavicular portion of the deltoid of man.
The =superficial pectoral= muscle is small. It arises on the sternum
from the first to the third costal cartilage, and is inserted into the
anterior surface of the humerus. A superficial slip detached from it is
inserted into the fascia of the forearm. The =deep pectoral= has no
prescapular portion. It arises on the sternum and costal cartilages from
the second costal to the xiphoid cartilage. It is inserted chiefly into
the internal tuberosity of the humerus, but also by small slips into the
external tuberosity and the fascia of the arm.
The =serratus magnus= shows no clear division into cervical and thoracic
portions. It arises from the last five cervical vertebræ and the first
seven or eight ribs, and is inserted into the upper part of the costal
surface of the scapula.
The =deltoid= is clearly divided into scapular and acromial parts, the
former arising on the spine, the latter on the acromion of the scapula.
Both end on the deltoid tuberosity.
The =supraspinatus= ends chiefly on the external tuberosity of the
humerus, but has a small attachment to the internal tuberosity also.
The =infraspinatus= is inserted into the outer surface of the external
tuberosity of the humerus.
[Illustration:
FIG. 232.—MUSCLES OF THORACIC LIMB OF DOG, INTERNAL VIEW.
(Ellenberger-Baum, Anat. des Hundes.)
]
The =teres minor= arises on a tubercle on the posterior border of the
scapula, just above the glenoid cavity, and is inserted into the deltoid
ridge.
The =subscapularis= is wide and is somewhat multipennate in structure,
being intersected by fibrous septa which are attached to the rough lines
on the costal surface of the scapula.
The =teres major= is thick. It arises on the upper part of the posterior
border of the scapula and on the subscapularis.
The =coraco-brachialis= is short and undivided, and is inserted into the
upper part of the postero-internal surface of the humerus.
The capsularis is absent.
[Illustration: