334 



AVES. 



the tongue (E, fig. 170\ the lower surface 

 of the mouth, and furnishes the artery which 

 enters the substance of the lower jaw. 



" Just at the origin of the submaxillary artery 

 there is another little branch of the carotid, 

 which is lost upon the muscles of the os 

 hyoides. 



" The internal maxillary artery is, as usual, 

 the continuation of the trunk of the external ca- 

 rotid ; it runs forwards between the pterygoid 

 mflscle, and the lining of the mouth, upon the 

 side of the long muscle for moving the upper 

 jaw, and divides into two principal branches; 

 one of them proceeds under the tendon of the 

 long muscle to get upon the palate, where it 

 forms two branches, of which one runs along 

 the external side of the palate, between the 

 membrane and the bone of the mandible to 

 the extremity of the bill, where it becomes 

 united to the same branch of the opposite side, 

 as also to the middle artery of the palate. The 

 other branch lies also superficially under the 

 membrane which lines the mouth. It passes 

 onwards to meet its corresponding vessel of 

 the opposite side, with which it becomes ac- 

 tually incorporated, and by their union a single 

 artery is generated, which runs along the mid- 

 dle line of the palate to the end of the mandi- 

 ble, where it unites with the lateral branches, 

 as already mentioned. At the junction of the 

 vessel of each side to form the middle pala- 

 tine artery, two branches go off, which are lost 

 upon the lining of the mouth, and the interior 

 of the organ of smell. 



" The other branch of the internal maxillary 

 artery is reflected upwards towards the orbit, 

 below which it divides and unites again, form- 

 ing a triangle, through which the vein passes : 

 at this place it produces a remarkable plexus 

 of vessels, like the rete mirabile of the carotid 

 artery of quadrupeds, which is increased by 

 branches from the ophthalmic and the palatine 

 arteries, and from which the back part of the 

 organ of smell receives its supply of blood. 



" The internal maxillary artery then runs direct- 

 ly backwards below the orbit, passes between the 

 radiated or fan-shaped muscle which moves 

 the upper jaw and the pterygoid process ; and 

 turning inwards round the basis of the cranium, 

 becomes incorporated with the internal carotid 

 artery just as it enters the bony canal which 

 conducts it to the brain.* 



" The vertebral artery (6), soon after it parts 

 from the carotid, sends off a branch backwards, 

 which passes over the neck of the scapula and 

 is lost among the muscles on the posterior part 

 of the shoulder, inosculating with the articular 

 and other arteries about the joint : this branch 

 might be called the supra-scapular (5). In the 

 duck we have observed it, before it makes the turn 

 over the scapula, to send an artery upwards 

 along the muscles of the neck. The trunk of 

 the vertebral artery proceeds obliquely upwards, 



* Barkow describes the internal maxillary artery 

 as wanting in birds, and its place being supplied by 

 branches of both the external and internal carotids 

 and the facial artery, all of which sometimes unite 

 to form the maxillary plexus of vessels, which is 

 very conspicuous in the Goose and Duck. 



and having entered the foramen in the transverse 

 process of the second cervical vertebra, gives off 

 a large branch downwards, which is distributed 

 between the vertebrae, and to the spinal canal, 

 in the manner of the intercostal arteries, with 

 which it anastomoses upon arriving in the 

 thorax. The remainder of the vertebral artery 

 is continued upwards in the canal formed in 

 the transverse processes of the cervical vertebrae, 

 diminishing gradually in consequence of the 

 branches it sends off between each vertebra to 

 the spinal marrow and the muscles of the neck. 

 Near the head the artery is found considerably 

 reduced, and within the last foramen in the 

 transverse processes terminates entirely by 

 inosculation with the reflected occipital branch 

 of the carotid, as before noticed. 



" The extraordinary anastomoses and the 

 plexuses which are to be observed in the arte- 

 ries of the head in birds are not easily ac- 

 counted for. It seems possible that they may 

 be required in consequence of the great length 

 of the neck in these animals, it being well 

 known that frequent communication amongst 

 the vessels, although it diminishes the impetus 

 of the circulation, ensures a free and uninter- 

 rupted motion of the blood. 



" After the common trunk of the carotid and 

 vertebral is detached from the arteria innominata, 

 this vessel may assume the name of the sub- 

 daman (14). While passing under the clavicle 

 it sends off some important branches : the first 

 might be called the pectoral artery; it proceeds 

 upwards upon the internal surface of the pec- 

 toralis minimus muscle, which it supplies, and 

 then dividing into two branches, one passes 

 over the anterior edge of the clavicle, and under 

 the pectoralis medius, between which and the 

 sternum it runs, detaching its branches to the 

 muscle ; the other sends first along the under 

 side of the clavicle a branch which is again 

 subdivided and distributed to the outside of 

 the shoulder-joint and to the deltoid muscle, 

 in which it inosculates with the articular artery. 

 The vessel then passes between the clavicle 

 and the fork-shaped bone, and on a ligament 

 which connects the head of the clavicle to that 

 of the scapula, and disperses its branches 

 upon the upper part of the shoulder-joint, form- 

 ing anastomoses with the neighbouring arteries. 



" The next branch of the subclavian is the 

 humeral artery (15); it arises from the upper 

 side of the vessel, and makes a slight curve 

 to reach its situation on the inside of the arm 

 in order to disperse its branches in the manner 

 hereafter described. 



" The internal mammary artery (24,/g. 171) 

 is given off just as the subclavian leaves the 

 chest. It divides into three branches; one 

 ramifies upon the inner surface of the sternum, 

 another upon the sternal ribs and the inter- 

 costal muscles, and the third runs along the 

 anterior extremities of the vertebral ribs, sup- 

 plying the intercostal muscles, &c. 



" The chief peculiarity of the arteries of the 

 superior extremities in birds consists in the 

 great magnitude of the vessels which supply 

 the pectoral muscles ; these, instead of being 

 inconsiderable branches of the axillary artery, 



