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. coUateralis 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 fasciae 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. coUateralis 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 

 carpi 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 clips 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 bj' the median nerve, which lies in front of the artery at its 

 origin, then usually crosses over it obliquely at the elbow j oint 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 arter j- ; 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 



' 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 vessel should be termed the median artery. 



* The pulse can be taken where the artery lies on the ligament, since the pectoral muscle ia 

 thin here. 



