196 ANATOMY OF VERTEBRATES. 



to the back of the jomt, upon wliich it ramifies and forms ana- 

 stomoses with the profunda humeri. The artery then proceeds 

 along the inner edge of the ulnar muscles, to which it distributes 

 branches. It is afterwards seen passing over the carpal bone of 

 the ulnar side, and under the annular ligament, at Avhich place it 

 sends off some branches which spread upon the joint and inosculate 

 ^dth the similar ones of the interosseous artery. Very soon after 

 the ulnar artery gets upon the metacarpus, it dips in between the 

 bones, and reappears u2)on the opposite side, lying under the 

 roots of the quills, to each of which it sends an artery ; it pre- 

 serves this situation to the end of the metacarpal bones, where it 

 passes between the style analogous to the little finger and the 

 principal or fore-finger, and pursues its course along the edge of 

 the latter, to the extremity of the wing, supplying each of the 

 true quills Avith an artery, and sending at each joint of the finger 

 a cross branch to communicate with the anastomosing branches 

 on the opposite side. 



' The interosseous artery detaches first a branch of some size to 

 the membrane which is spread in the fold of the wing, upon which 

 it forms several ramifications, fig. 94, o. After this the artery 

 dips down behind the flexor muscles to get into the space between 

 the ulna and radius. It here gives a branch backward to com- 

 municate ^\ii\\ the others about the joint, and proceeds in the inter- 

 osseous space as far as the carpal joint, during which course they 

 become much diminished from o-ivino- off several branches which 

 are distributed to the integuments and the quills placed upon the 

 outside of the ulna. The remainder of the interosseous artery is 

 expended in small branches upon the back of the carpal joint, the 

 bastard quills, and along the radial edge of the metacarpal and 

 bones of the fore-finger, Avhere it forms communications Avith the 

 cross branches of the ulnar artery already mentioned. 



^ From this description it Avill be perceived that no artery exists 

 in birds strictly analogous to the radial ; that there are no i)almar 

 arches ; and that the size of the interosseous artery, and the 

 course of the ulnar, along the outside of the metacarpus, are 

 peculiarities which arise from the necessity of affording a large 

 supply of blood to the quills during their growth. 



' The descending aorta, fig. 93, 19, makes a curve round the 

 right auricle and right bronchus, in order to get upon the pos- 

 terior surface of the heart, after which its course is close along the 

 spine, in which situation it is bound down by cellular substance, 

 and the strong membrane or aponeurosis, which covers the lungs 

 on their anterior j)art. The first branches which this vessel 



