656 THE ARTERIES. 



the posterior interosseous arteries of the metacarpus, after giving off on each side 

 two other ramuscules that wind round the borders of the large met;) carpal bone, 

 receiving the dorsal interosseous arteries, and ramify in front of the fetlock, on 

 the anterior face of the cannon bone, and in the texture of the capsular ligament 

 of the metacarpo-phalangeal articulation (Figs. 376, 10 ; 378, 11). 



Terminal branches. — These are, as we said, the digital arteries, which almost 

 exactly repeat the disposition of these vessels in the posterior limb, and which 

 have been described at p. 036. 



Differential Characters in the Axillary Arteries of the other Animals. 



1. Axillary Arteries of Ruminants. 



Thf se vessels comport themselves in their origin, course, and relations, as in Solipeds. 

 The special characters they present in their distribution are as follows : — 



1. Dorsal artery. — This arises from a trunk common to it and the vertebral artery, and 

 usually leaves the thorax by passing above the first costo-vertebral articulation. Its subcostal 

 branch proceeds directly from the above-named trunk. 



2. Superior cervical artery. — This is absent, and is replaced by a branch of the dorsal artery, 

 but particularly by the superior muscular divisions of the vertebral artery. 



3. Vertebral artery. — Extremely voluminous, and terminates in the muscles of the neck, 

 after passing through the foramen of the axis ; it is remarkable for the considerable size of its 

 spinal branches. 



4. Inferior cervical, and internal and external thoracic arteries. — Tiiese do not present 

 anything worthy of special consideration, except that the last is very voluminous in the Ox 

 and very slender in the Sheep, and supplies the satellite arterial branch of tlie ceplialic vein, 

 which, in Solipeds, arises from the inferior cervical artery. 



5. Supra-scapular artery. — This vessel appears to us to be absent in the Sheep, and its place 

 supplied by the divisions of the inferior cervical artery. 



6. Subscapulary artery. — The scapulo-humeral branch gives off the majority of the branches 

 for the posterior brachial muscles. 



7. Humeral artery. — The muscular arteries are of small size, particularly the deep humeral, 

 which is largely replaced by the scapulo-humeral branch. 



8. Anterior radial artery. — This comports itself similarly to that of the Horse, and is liable 

 to as frequent anomalies. 



9. Posterior radial artery. — This artery follows the same course as in Solipeds; only 

 instead of furnishing the radio-palmar artery near the carpus, at the point where it becomes 

 the collateral artery of the cannon, it gives off that vessel much higher, and near the upper 

 third or middle of the forearm. Its interosseous branch, lodged in the deep channel on tho 

 outside of the bones of this region, where the radius and ulna join, is separated into two 

 branches near the inferior extremity of that groove. The anterior of these ramifies on the 

 dorsal face of the carpus, and anastomoses with the division of the anterior radial artery; the 

 posterior traverses the inferior radio-ulnar arch, to distribute the majority of its branches 

 behind the carpal articulations. 



10. Radio-palmar artery.— Anaing, as we have already seen, from the posterior radial 

 artery, towards the upper third of the forearm, this branch descends to the superior extremity 

 of the metacarpus in following, as in the Horse, a superficial course, and ends in four meta- 

 carpal interosseous arteries : three posterior or palmar, and one anterior or dorsal. The posterior 

 interosseous arteries are very irregular and inconstant in their disposition; they communicate 

 witli each i)ther by several branches, and anastomose, inferiorly, either with the lateral digital 

 ftrteries, the collateral of the cannon, or, as is most commonly the case, with a brancli of the 

 latter vessel. These interosseous arteries are distinguislied into external, middle, and internal ; 

 the first two are comprised between the posterior face of the metacarpus and the suspensory 

 ligament ; the third, placed at the inner border of that ligament, is more considemble than 

 the others, and by its volume and direction represents the continuation of the radio-palmar 

 artery. The anterior interosseous artery passes through the foramen at the superior extremity 

 of the metacarpus, and, arriving at the dorsal face of the bone, bifurcates, its ascending branch 

 reaching the capsular ligament of the carpal articulations, where it anastomoses with the 

 divisions of the anterior radial and interosseous arteries of the forearm ; the descending is 

 lodged in the anterior groove of the metacarpal bone, and joins a perforating branch of the 



