_A_, Brachial artery; _B_, subscapular artery; _C_, thoracico-dorsal
artery; _D_, deep brachial artery; _E_, ulnar artery; _F_, anterior
radial artery; _G_, posterior radial (or median) artery; _H_,
brachial vein; _I_, external thoracic (or “spur”) vein; _J_,
brachial vein; _K_, _K_, _K_, posterior radial veins; _L_, cephalic
vein; _L′_, communicating vein; _M_, brachialis muscle; _N_,
internal epicondyle of humerus; _O_, prescapular lymph glands; _P_,
position of axillary lymph glands; _Q_, position of cubital lymph
glands; _1_, suprascapular nerve; _2_, subscapular nerves; _3_,
thoraco-dorsal nerve; _4_, musculo-cutaneous nerve; _4′_, cutaneous
branch of musculo-cutaneous nerve; _5_, median nerve; _6_, axillary
nerve; _7_, ulnar nerve; _8_, radial nerve; _9_, thoracic nerves.
(After Schmaltz, Atlas d. Anat. d. Pferdes.)
]
[Illustration:
FIG. 442.—DISSECTION OF RIGHT FOREARM AND CARPUS OF HORSE, INTERNAL
SURFACE.
_C.b._, Coraco-brachialis muscle; _E.m._, internal epicondyle of
humerus; _R_, subcutaneous surface of radius. (After Schmaltz, Atlas
d. Anat. d. Pferdes.)
]
3. The =anterior circumflex= (or prehumeral) =artery= (A. circumflexa
humeri anterior) arises usually at the upper border of the teres major.
It passes forward and outward between the two parts of the
coraco-brachialis or between the latter and the humerus. It gives
branches to the coraco-brachialis and deep pectoral and ends in the
upper part of the biceps and in the mastoido-humeralis. It anastomoses
with the posterior circumflex.
Not rarely it arises below the middle of the humerus and passes upward
between the biceps and coraco-brachialis. In these cases a small
branch for the coraco-brachialis is usually given off at the usual
point of origin of the anterior circumflex.
4. The =deep brachial artery= (A. profunda brachii) is a large but short
trunk which arises usually about the middle of the humerus. It passes
backward and divides into several branches which supply the triceps,
tensor fasciæ antibrachii, anconeus, and brachialis. A branch runs in
the musculo-spiral groove with the radial nerve to the front of the
elbow joint and anastomoses with the anterior radial. A slender branch
passes down along the external border of the extensor carpi and supplies
cutaneous twigs. Anastomoses occur with the ulnar and recurrent
interosseous arteries.
The point of origin is inconstant and it is not uncommon to find two
arteries instead. Often a large branch for the posterior deep pectoral
muscle is detached close to the origin or arises from the brachial
directly.
5. =Muscular branches= (Rami musculares) are distributed to the teres
major, deep pectoral, coraco-brachialis, and biceps. The largest and
least variable of these supplies the lower part of the biceps.
6. The =ulnar artery= (A. collateralis ulnaris superior) arises a little
below the nutrient foramen of the humerus and passes downward and
backward along the lower edge of the internal head of the triceps under
cover of the brachial vein and the tensor fascia antibrachii. It gives
branches to these muscles, the posterior superficial pectoral, the
cubital lymph glands, panniculus, and skin. At the internal epicondyle
of the humerus it is joined by the ulnar nerve and turns downward under
the ulnar head of the flexor carpi medius. It continues with the vein
and nerve under the deep fascia of the forearm between the ulnar and
humeral heads of the perforans, and in the distal half of the region
between the external and middle flexors of the carpus. It unites just
above the carpus (under cover of the flexor carpi externus) with a
branch of the radial artery, with which it forms the supracarpal arch.
It detaches small collaterals to the muscles along which it passes and
terminal twigs to the outer surface of the carpus.
7. The =nutrient artery of the humerus= (A. nutritia humeri) is a short
vessel which enters the nutrient foramen of the humerus. It often arises
from the ulnar.
8. The =anterior radial artery= (A. collateralis radialis inferior)
passes downward and a little outward on the anterior face of the humerus
under cover of the biceps and brachialis to the front of the elbow
joint, where it is joined by the radial nerve. It then descends on the
anterior surface of the radius under cover of the anterior extensor of
the digit to the carpus, where it concurs in the formation of the rete
carpi dorsale, anastomosing with the posterior radial and interosseous
arteries. It supplies branches to the elbow joint, the biceps,
brachialis, and the extensors of the carpus and digit. A cutaneous
branch emerges between the distal end of the biceps and the brachialis.