AVES. 



335 



are the continuations of the trunk of the sub- 

 clavian, of which the humeral is only a branch. 

 "The great pectoral or thoracic artery passes 

 out of the chest over the first rib and close to 

 the sternum, and immediately divides into two 

 branches. One of them (16) ramifies in the 

 superior part of the pectoral is major, and the 

 other (17) is exhausted in the lower part of the 

 muscle, and sends off a branch analogous to 

 the long thoracic artery of mammalia." Nos. 16 

 and 17 show the distribution of these arteries to 

 the skin after perforating the pectoralis muscle. 

 " The humeral artery, while within the axilla, 

 gives a small branch backwards to the muscles 

 under the scapula, and upon reaching the 

 inside of the arm produces an artery that soon 

 divides into the articular and the profunda 

 humeri. The articular artery passes round the 

 head of the humerus, underneath the extensors; 

 its branches penetrate the deltoid muscle, and 

 anastomose with the other small arteries around 

 the joint. 



" The profunda humeri, as usual, turns under 

 the extensor muscles to reach the back of the 

 bone, at which place, in birds, it separates into 

 two branches, of which one descends upon the 

 inside, and the other upon the outside of the 

 articulation of the humerus with the radius and 

 ulna, and there inosculate with the recurrent 

 branches of the arteries of the fore-arm. 



" After the humeral artery has sent off the pro- 

 funda, it descends along the inner edge of the 

 biceps muscle, detaching some branches to the 

 neighbouring parts : upon arriving at the fold 

 of the wing, it divides into two branches ; one 

 of these is analogous to the ulnar artery, and 

 the other from its position deserves to be called 

 rather the intcrosseous than the radial artery. 



" At the place where the humeral produces 

 the two arteries of the fore-arm, a small branch is 

 sent off, which is lost upon the fore-part of the 

 joint, and in anastomoses with the recurrent of 

 the ulna and profunda humeri. 



" The ulnar artery is the principal division of 

 the humeral ; it proceeds superficially over the 

 muscles which are analogous to the pronator, 

 sends a large recurrent branch under the flexor 

 ulnaris to the back of the joint, upon which it 

 ramifies and forms anastomoses with the pro- 

 funda 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 which place 

 it sends off some branches which spread upon 

 the joint and inosculate with the similar ones 

 of the interosseous artery. Very soon after the 

 ulnar artery gets upon the metacarpus, it dips 

 in between the bones, and re-appears upon the 

 opposite side, lying under the roots of the 

 quills, to each of which it sends an artery ; it 

 preserves this situation to the end of the meta- 

 carpal 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 with an artery, 

 and sending at each joint of the finger a cross 



branch to communicate with the anastomosing 

 branches on the opposite side. 



" The intcrosseous artery detaches first abranch 

 of some size to the membrane which is spread in 

 the fold of the wing, upon which it forms several 

 ramifications. (See o, Jig. 171.) After this the 

 artery dips down behind the pronator muscles to 

 get into the space between the ulna and radius. 

 It here gives a branch backwards to communi- 

 cate with the others about the joint, ^and pro- 

 ceeds in the interosseous space as far as the 

 carpal joint, during which course they become 

 much diminished from giving off several 

 branches which are distributed to the integu- 

 ments 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 metacarpus and 

 bones of the fore-finger, where it forms com- 

 munications with the cross branches of the 

 ulnar artery already mentioned. 



" From this description it will be perceived 

 that no artery exists in birds strictly analogous 

 to the radial ; that there are no palmar 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 (W,fg. 170) makes 

 a curve round the right auricle and right 

 bronchus, in order to get upon the posterior 

 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 part. The first 

 branches which this vessel appears to send off 

 are bronchial arteries ; they arise from the fore 

 part of the aorta, just when it arrives upon the 

 spine ; and having entered the lungs, their ra- 

 mifications accompany those of the pulmonary 

 arteries. They appear also to send branches to 

 the spine and the spaces between the ribs. 



" The intercostal arteries do not take their 

 origin from the aorta in numerous and regular 

 branches as in mammalia, but consist originally 

 of but few vessels, which are multiplied by 

 anastomoses with each other, and with the 

 arteries which come out of the spinal canal. 

 An arterial plexus is thus formed round the 

 heads of the ribs, from which a vessel is sent 

 to each of the intercostal spaces. Many of 

 these branches, besides supplying the intercos- 

 tal muscles and ribs, are continued into the 

 muscles upon the outside of the body and the 

 integuments. The anastomosis of the inter- 

 costal arteries round the ribs is very similar to 

 the plexus, which is produced by the great 

 sympathetic nerve in the same situation. 



" The aorta produces no branch which de- 

 serves the name of the phrenic artery, as birds 

 do not possess that muscular septum of the 

 body to which the artery of this name is dis- 

 tributed in other animals. 



"The cceliac artery (20, fig. 170) is a very large 

 single trunk, and arises from the fore part of the 



