BRANCHES OF THE IXTEROSSEOUS ARTERY. 391 



The anterior interosseous artery gives off the folloAving branches : 



(a) The artery of the median nerve, or the median artery, a long slender branch, 

 which accompanies the median nerve and sends offsets into its substance. This 

 artery is sometimes much enlarged, and in that case it presents several peculiarities 

 to be hereafter noticed. 



(b) Muscular branches to the flexor profundus, flexor longus pollicis, and pronator 

 quadratus muscles. 



(e) The nutrient arteries of the shafts of the radius and ulna, which, diverging from 

 one another, enter the oblique foramina in those bones to be distributed to the 

 medullary membrane in their interior. 



(d) An anterior inosculating branch, given off before the artery pierces the inter- 

 osseous membrane, and descending beneath the pronator quadratus muscle to anas- 

 tomose with the anterior carpal arteries. 



(e) Terminal twigs inosculating with the posterior carpal arteries. 



The posterior interosseous artery passes backwards through the interval 

 left between the oblique ligament and the upper border of the interosseous 

 ligament, and continuing its course downwards along the fore-arm, covered by 

 the superficial layer of extensor muscles, gives branches to them and the 

 deep-seated muscles, and reaches the carpus considerably diminished 

 in size. 



In addition to muscular branches, it gives off the following : 



(a) The posterior interosseous recurrent, which passes directly upwards, covered by 



the anconeus, to reach the interval between the olecranon and external condyle ; at 



which place it divides into several offsets which anastomose with the superior profunda 



and the posterior ulnar recurrent. 



(6) Terminal branches, which anastomose with the posterior or terminal branch 



of the anterior interosseous artery, and with the carpal branches of the radial and 



ulnar arteries. 



MUSCULAR BRANCHES of the ulnar artery are distributed to the muscles 

 in the course of the vessel along the fore-arm : some of these perforate the 

 interosseous ligament to reach the extensor muscles. 



CARPAL BRANCHES. The posterior ulnar carpal branch, of variable size, 

 arises a little above the pisiform bone, and, winding back under the tendon of 

 the flexor carpi ulnaris, reaches the dorsal surface of the carpus beneath the 

 extensor tendons. 



Its branches are the following. 



(a) A branch anastomoses with the posterior carpal artery derived from the 

 radial, so as to form the posterior carpal arch; from this arch are derived the 

 second and third dorsal interosseous arteries, which descend on the spaces between 

 the third and fourth and the fourth and fifth metacarpal bones, and are reinforced 

 at the upper ends of those spaces by anastomoses with the posterior perforating 

 branches of the deep palmar arch. 



(I) A branch runs along the metacarpal bone of the little finger. Sometimes this 

 metacarpal branch arises as a separate vessel, the posterior carpal being then very 

 small. 



The anterior ulnar carpal branch is a very small artery, which runs on the 

 anterior surface of the carpus beneath the flexor profundus, anastomoses 

 with a similar offset from the radial artery, and supplies the carpal bones 

 and articulations. 



PECULIARITIES. Origin. In the whole number of cases observed by Richard 



Quain, the ulnar artery was found to deviate from its usual mode of origin, nearly in 



the proportion of one in thirteen. The brachial artery was, more frequently than the 



xillary, the source from which it sprang; indeed, the examples of its origin from the 



main trunk at different pirts appeared to decrease in number in proportion as the 



