654 BLOOD-VASCULAR SYSTEM OF THE HORSE 
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 distal part of the biceps. 
6. The ulnar artery (A. collateralis ulnaris proximalis) arises at the distal 
end of the coraco-brachialis and passes downward and backward along the ventral 
edge of the medial head of the triceps under cover of the brachial vein and the 
tensor fascie antibrachii. It gives branches to these muscles, the posterior super- 
ficial pectoral, the cubital lymph glands, cutaneus, and skin. At the elbow it lies 
on the posterior part of the medial epicondyle, in relation in front to the ulnar 
nerve, and largely covered by the satellite vein; it then turns downward under the 
ulnar head of the flexor carpi ulnaris. It continues its descent with the vein and 
nerve under the deep fascia of the forearm between the ulnar and humeral heads of 
the deep flexor of the digit, and in the distal half of the region between the lateral 
and middle flexors of the carpus. It unites just above the carpus (under cover of 
the flexor carpi ulnaris) with a branch of the median artery, with which it forms the 
supracarpal arch. It detaches small collaterals to the muscles along which it passes 
and terminal twigs to the lateral 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 distalis)! 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 in contact with the radial 
nerve. It then descends on the anterior surface of the radius, under cover of the 
common digital extensor, to the carpus, where it concurs in the formation of the rete 
sarpi dorsale, anastomosing with the median and dorsal 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. 
THE MEDIAN ARTERY 
The median or posterior radial artery (A. mediana)? is the direct continuation 
of the brachial. It descends, inclining slightly backward, at first on the medial 
surface of the humerus, and then over the capsule and medial ligament of the elbow 
| 
joint, under cover of the posterior superficial pectoral muscle. At the proximal | 
third of the forearm it dips under the flexor carpi radialis and passes down the medial 
part of the posterior surface of the radius. In the distal part of the forearm it — 
inclines backward and is separated from the radius by the reinforcing band (Caput | 
tendineum) of the superficial flexor of the digit and is continued by the common | 
digital or large metacarpal artery. 
It is accompanied by the median nerve, which lies in front of the artery at its 
origin, then usually crosses over it obliquely at the elbow joint and becomes posterior. 
At the distal end of the arm the artery is crossed by the large anastomotic vein | 
which connects the cephalic and brachial veins, and a radicle of the brachial vein lies 
behind and partly upon the artery; lower down there are usually two satellite 
veins, anterior and posterior. The chief collateral branches are as follows: 
1. Articular branches are supplied to the elbow joint. 
2. Muscular branches go to the flexors of the carpus and digit; the largest of — 
these arise at the proximal third of the forearm. | 
3. The common interosseous artery (A. interossea communis) is a vessel of | 
} 
1 This vessel is apparently the A. transversa cubiti of comparative anatomy. 
2 Although the homology of some arteries in this region are still unsettled, it seems clear that | 
this oe should be termed the median artery. 
- ee pulse can be taken where the artery lies on the ligament, since the pectoral muscle is | 
thin here. 
