ARTERIES OF BIRDS. 195 



one ramifies upon the inner surface of the sternum, another upon 

 the sternal ribs and the intercostal muscles, and the thu'd runs 

 along the anterior extremities of the vertebral ribs, supplying the 

 intercostal muscles, &c. 



' The chief peculiarity of the arteries of the superior extre- 

 mities in birds consists in the great magnitude of the vessels which 

 supply the pectoral muscles ; these, instead of being inconsider- 

 able branches of the axillary artery, are the continuations of the 

 trunk of the subclavian, 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, fig. 93, 16, ramifies in 

 the superior part of the pectoralis major, and the other, ib. 17, is 

 exhausted in the lower part of the muscle, and sends off a branch 

 analogous to the long thoracic artery of MammaUa.' Fig. 93 

 shows the distribution of these arteries to the skin after per- 

 forating the pectoralis muscle. 



' The humeral artery, while within the axilla, gives a small 

 branch backward to the muscles under the scapula, and uj^on 

 reaching the inside of the arm produces an artery that soon 

 divides into the articular and the profunda humeri. The articu- 

 lar artery passes round the head of the humerus, underneath the 

 extensors ; its branches penetrate the deltoid muscle, and ana- 

 stomose 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 profunda, it descends 

 along the inner edge of the biceps muscle, detaching some branches 

 to the neighbouring parts ; upon arri^dng 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 interosseous than tlie 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 



o 2 



