THE BRACHIAL OB AXILLARY AETEBIES. 575 



and an external and internal collateral of the elbow (collateralis ulnaris superior and 

 inferior). In the lower third of the arm, the brachial artery is comprised between 

 tiie braohialis anticus and inner border of the biceps ; so that, during' flexion, and 

 especially active and forced flexion, of the fore-arm on the arm, in vigorous subjects, the 

 circulation is arrested in the vessels of the hand. 



The radial artery of Man is represented in the Horse by the posterior radial artery. 

 It is directed downward and a little inward, supposing the hand to he in a state of 

 pronation ; it crosses the carpus in front of the trapezium and scaphoides, at the bottom 

 of the anatomical snuff-box, and beneath the flexor tendons of the phalanges forms the 

 deep palmar arch, finally anastomosing with a branch of the ulnar at the hypothenar 

 eminence. Along its course it furnishes muscular branches : the earpea anterior; radio- 

 palmar, which passes outwards, and unites with a branch of the ulnar artery to form the 

 superficial palmar artery ; the dorsalis poUieis ; the carpea posterior, wliich concurs in 

 the formation of the dorsal arch of the carpus that gives origin to the dorsal interosseous 

 branches. 



The ulnar artery, formed, in Solipeds, by the anterior radial, passes downward and 

 outward; it is at first covered by the great pronator muscles, great and small palmar, 

 and superficial flexor ; lower, it is only protected by the antibraohial aponeurosis ami 

 the skin. On the anterior face of the carpus, it passes witlun the pisiform bone, and 

 anastomoses with the radio-palmar artery, whence results the superficial palmar arch. 

 It gives rise to two recurrent arteries that ascend to receive the collateral vessels of the 

 elbow, then to a trunk seen in animals, and which divides into the anterior and posterior 

 interossese. 



The three arches that exist in the vicinity of the carpus, the constitution of which 

 has been already given, are distributed in the following manner 



The superficial palmar arch is situated at the surface of the flexor tendons ; from its 

 convexity it emits four or five metacarpal branches : the first reaches tlie external 

 border of the little finger as the external collateral of that organ the other four 

 are lodged in the interosseous spaces, and wlien tliey reach the roots of the fingers 

 they bifurcate and constitute the external or internal collateral arteries of the five fingers. 

 The deep palmar arch furnishes : articular branches to .the wrist, the perforating Iranches 

 which cross the interosseous spaces to unite with the dorsal interossese ; the palmar 

 interossese, which join the superficial interossese before their division into collateral 

 branches. Lastly, the carpal dorsal arch gives off tlie dorsal interossese, which receive 

 perforating filaments above and below the metacarpus, and are expended in the 

 articulations and skin of the fingers. 



Article VII. — Primitive (ok Common) Carotid Arteries. 

 (Figs. 282, 14 ; 286, 1.) 



Origin.— These two vessels (named from Kopa., the head) arise from the 

 right axillary artery, at a short distance from its origin, by a common 

 trunk, the cephalic, which is detached at a very acute angle, and is directed 

 forward beneath the inferior face of the trachea, and above the anterior vena 

 cava, to terminate near the entrance to the chest by a bifurcation that 

 commences the two common carotids. 



Course.— 'Ea.ck of these arteries afterwards ascends in the midst of an 

 abundant, though dense, connective tissue, along the trachea, at first beneath 

 that tube, then at its side, and finally a little behind its lateral plane. 

 Each carotid arrives in this way at the larynx and guttural pouch, where it 

 divides into three branches. 



Belations.— In its course, this vessel, independently of the connection 

 between it and the trachea, affects the following relations :— 



Throughout its entire length, it is accompanied by the cord that results 

 from the union of the pneumogastric nerve with the cervical portion of tho 

 sympathetic, and by the recurrent nerve ; the latter is placed below or in 

 front of the vessel, from which it is somewhat distant in the lower part of 

 the neck ; the first is situated above or behind the artery, and lies close to 



it. 



It also corresponds : behind, in its upper two thirds, to the longus colli 



