THE DISTRIBUTION OF ARTERIES. 131 



passes between the ulna and radius (Fig 10 . k). The radial 

 artery (Fig 10 . /, I), which proceeds downwards, to nurture 

 the flexor muscles ; sends off a branch to nourish the 

 medullar of the radius (Fig 10 . m) ; and another near the 

 knee, called the small metacarpal artery (Fig 10 . n). The 

 main trunk is then continued downwards under the mus- 

 cles, behind the radius ; then passes within the arch of the 

 trapezium; and becomes the metacarpal artery (Fig 10 . o, o) ; 

 which continues down under the nerve upon the inner 

 side of the leg. At the lower part of the cannon it divides 

 just above the fetlock into the two plantar vessels. The 

 ulnar arteries (Fig 10 . k, k) go to the joint and muscles 

 about the bone ; while the spiral, sent off a little above the 

 ulnars (Fig 10 . j), is mainly distributed to the extensors of 

 the limb. 



The two arteries, which are formed by the ultimate 

 division of the metacarpals, are called the plantar arteries ; 

 and each of them passes upon the side of the pastern bone. 

 When they reach the foot they are at the back of it ; and 

 each sends a branch to the fatty frog ; while the main trunks 

 pursue their course along the inner surface of the wings of 

 the coftin bone ; to unite with each other, and form an arte- 

 rial circle within the substance of the bone of the foot. From 

 the arterial circle thus formed are sent off various small 

 twigs ; which penetrate the porous coffin bone, and then bend- 

 ing downward unite and form the circumflex artery ; which 

 runs round the margin of the bony sole, to which blood from 

 the circumflex artery is transmitted. Of course there are 

 small branches also sent to nourish every part through which, 

 or near to which, the arteries run ; but from the fear of ren- 

 dering our description too complex, we have omitted very 

 much, which the reader, probably with justice, would con- 

 sider mere dry detail. 



The carotid, common trunk (Fig Q . 8), arises from the 

 right arteria innominata, and even this vessel sometimes 

 divides into two portions. Each carotid is a very long 

 vessel, whereby the strong action of the heart is counter- 

 acted ; and the head of the horse is less liable to congestion 

 than man's, in whom these vessels are so much shorter. 

 As it approaches the head, it divides into what are termed 

 the external (Fig 11.7) and internal carotids (Fig 11 . 6), 



k2 • 



