THE BRACHIAL OR AXILLARY ARTERIES. 65& 



Ulnar artery. — Much smaller than the radial, this vessel gives off, near its origin, the 

 interosseous artery, which soiueiimes proceeds tlirtctly from tlie humeral artery, and the onlibro 

 of which always exceeds, in animals, that of the ulnar artery. The latter is directeil obliquely 

 outwards and downwards, passing under the perforans, and gains the internal face of the 

 anterior ulnar or oblique Hexor of the metacarpus, where it lies beside the ulnar nerve, to 

 descend with it inside the unciform bone, and join the posterior interosseous artery, or one of 

 its terminal branches. On its track it gives oti' a number of muscular or cutaneous branches, 

 several of which anastomose with the internal collateral artery of the elbow, as well as with 

 divisions of the radial artery. 



Interosseous artery — This artery is placed between the ulna and radius, underneath the 

 pronator quadratus, aud is prolonged to the lower third of the forearm, where it separates 

 into two branches — the anterior and poMerior interosseous arteries, after throwing off oti its 

 way several branches, mostly anterior, which enter t)ie antibrachial muscles by traversing the 

 space comprised between the two bones of the forearm, the principal escaping by the radio- 

 ulnar arch. 



The anterior interosseous artery, after pa>sing between the radius and ulna, descends on 

 the anterior face of the carpus, where its divisions meet, inwardly, the collateral ramuscules 

 of the radio-palmar artery, and outwardly, the arborizations of a branch from the posterior 

 interosseous artery, forming with these vessels a wide-meshed plexus, from which definitely 

 proceed several tilainents that join the dorsal interosseous iiietacarj)al arteries. 



The posterior i)iteroi<seous artery may be regarded, by its volume and direction, as the 

 continuation of the interosseous trunk. After emerging from beneath the pronator (juadratus, 

 it detaches an internal flexuous branch anastomosing with the radio-palmar artery, then 

 several external musculo-cutaneous branchvs; after which it is placed within the pisiform 

 bone, where it divides into two branches, after receiving the ulnar artery. The smallest of 

 these branches anastomoses by inosculation with the superficial palmar arch ; the other, larger 

 and deeper seated, is carried in front of the flexor tendons, beneath the aponeurosis covering 

 the interosseous muscles, across tlie superior extremity of these, and so forming the deep 

 palmar arch, which unites witli a thin filament from the radio-palmar artery. This arch 

 supj)lies. witii some ramuscules destined to the muscles of the hand (or paw), eigld interosseous 

 metacarpal arteries^our posterior or palmar, wliich are united by their inferior extremity 

 with the collaterals of the digits, after giving several divisinns to the muscles of the hand ; and 

 four anterior or dorsal, traversing the superior extremity of the intermetacarpal spaces, like 

 the perforating arteries in Man, joining the anterior interosseous branches of the forearm, and 

 descending afterwards into tlie intermetacarpal spaces, to unite with the collateral arteries of 

 the digits at the metacarpo-phulangeal articulations 



Radial artery — tlie /josfer^'or rar?/a? of the other animals. Lying alongside the long flexor 

 of tlie thumb and the perfnrans muscle, this artery follows the inner face of the perforatus 

 muscle, and curving outwards to be united to a branch from the posterior antibrachial iuter- 

 osstous artery, formg the superficial palmar arch, from which escape four branches — the 

 pahnars or collaterals of the digits. These are at first situated between the perforatus and 

 perforaiis tendons, and reach tlie superior extremity of the interdigital spaces, wiiere they 

 receive the metacarpal interosseous arteries, and comport themselves in the following manner : 

 the internal goes to the thumb; the second — counting fmm within outwards— gains the con- 

 centric side of the index; the third, the largest, divides into two branches which lie alongside 

 the great digits ; the last goes to the external digit. 



Comparison of the Axillary Arteries in IMan with those of Animals. 



The arteries of the thoracic limbs and head arise separately from the arch of ihe aorta ; 

 consequently, in Man there is no anterior aorta. 



The vessel of the limb that re[)resents the axillary of animals is here resolved into two 

 portions : the subclavian artery and axillary artery. 



The Subclavian Artery has not the same origin on both sides ; on the right it arises 

 from the aorta by a trunk common to it and tlie carotid of that side — the arteria innominata ; 

 while the left is detached separately from the most distant part of the aortic arch. The 

 subclavian vessels extend to the inferior border of the clavicles, and furnish seven important 

 collateral branches, which are present in the domesticated animals. They are — 



1. The vertebral artery, situated in the vertebral foramina of the cervical vertebrae, as far 

 as the axis ; there it anastomoses, as in Solipeds, with a branch of the carotid, enters the 

 spinal canal by the foramen magnum, and unites with its fellow at the lower border of the 

 ])on8 Varolii to form the basilar artery which, in the Horse, comes from the cerebro-spinal 

 artery of the occipital. 



