THE ARTERIES 171 



major and latissimus dorsi muscles and close to where the musculo-spiral 

 nerve disappears from view in front of the caput muscle. After a very 

 short course the deep humeral artery spHts up into branches which are 

 distributed to the middle and small heads of the triceps muscle and a 

 long and slender branch which passes in front of the caput muscles in 

 company with the musculo-spiral nerve, the course of which it follows 

 round the musculo-spiral groove to reach the front of the elbow joint. 

 Here this branch anastomoses with the branches of the anterior radial 

 artery. The deep humeral artery supplies also the extensor metacarpi 

 magnus and the brachialis anticus muscles. 



(3) The Nutrient Artery to the Humerus is frequently given off as a 

 collateral branch of the brachial, although most commonly it is a branch 

 of the ulnar artery. It leaves the parent vessel between the middle and 

 lower thirds of the humerus and passes direct to the nutrient foramen 

 of the bone which is here situate. 



(4) The Ulnar Artery. — x^lthough not of great calibre, this vessel is 

 of considerable length. It leaves the brachial trunk near the nutrient 

 foramen of the humerus, and passes backwards on the bone itself. It 

 then takes an oblique course downwards and backwards along the 

 inferior border of the small head of the triceps muscle until it reaches 

 the ulnar nerve, which it accompanies to the inner aspect of the 

 olecranon process of the ulna. The artery vein and nerve are here 

 covered by the thin scapulo-ulnaris muscle. It next passes beneath the 

 tendon of origin of the flexor metacarpi medius, and descends the 

 forearm by following the tendon of the ulnar division of the flexor 

 perforans. It is found beneath the fibrous aponeurosis of the forearm, 

 between the middle and external flexors of the metacarpus. Just above 

 the carpus the ulnar artery terminates by anastomosing with a branch of 

 the posterior radial artery, and thus forming what is known as the supra- 

 carpal arch. 



During its course the ulnar artery gives off muscular branches to the 

 caput muscles (large and middle heads) and to the superficial pectorals, 



