STRUCTURE AND DISEASES OF THE HORSE’S FOOT. 365 
in the horse by two muscles. One of these, called the extensor of the 
pastern, is inserted by a strong tendon into the side of the first phalanx, 
the pastern-bone. The second muscle, placed between the two preceding 
muscles, furnishes a strong tendon which passes down in front of the 
carpus and becomes united with the communis at an acute angle. The 
anited tendon (Fig. 14, “5” ) passes behind the coronary border of the 
hoof to its insertion in the coffin-bone. The office of these muscles is 
to extend the foot upon the leg. Another muscle, the edductor longus 
pollicis, called in hippotomy the oblique extensor of the cannon, by its 
insertion into the base of the cannon-bone, acts as an extensor of the 
foot. 
A similar arrangement exists in the muscles of the hind leg. The 
tendon of the plantaris, of great strength, has a divided insertion cor- 
responding to that of the flexor sublimis perforatus of the fore leg, while 
the fleror perforans sends its single strong tendon between the two 
divisions of the preceding muscle to be inserted into the terminal pha- 
janx. These flexors of the foot are assisted by the tendon of the flexor 
hallucis, which unites with the tendon of the perforans. 'The extensor 
tendon of the hind leg, of great strength, is furnished mainly by the 
extensor communis muscle. The extensor brevis is represeated by a few 
fibers which come from the cannon-bone, and unite with the tendon of 
the communis. The united tendon passes, as the corresponding one of 
the fore leg, (Fig. 14, “5,”) to its insertion in the coflin-bone, — 
The arteries of the foot are branches of the radial, in the fore, and of 
the tibial in the hind legs. The former descends along the radius, 
accompanied by the radial nerve, to a point a littie above the knee, 
where it divides into the large and small metacarpal arteries. Of 
these the large metacarpal is the principal trunk, passing under the 
posterior annular ligament. While passing down the cannon-bone it 
divides into three branches. The middle one is distributed to surround- 
ing tissues, while the cther two become the plantar arteries, internal 
and external. The plantar arteries of the fore leg result from a divi- 
sion of the metacarpal, and in the hind leg from a similar division of the 
metatarsal, and the terminal distribution is alike in both. They descend to 
the lower part of the cannon-bone, (Fig. 15*, “19,” “20,” ““21,”) pass the 
fetlock joint by the side of the sesamoid bones, in company with veins 
and nerves of the same names, and pass into the substance of what is 
sometimes called the fatty frog. They then pass the extremities of the 
cofiin-bone and enter the foramina on the posterior concavity of the 
bone. (Fig. 16, a, a, a, a.) The branches of the plantar arteries are 
very numerous, and no part of the body is more fully supplied with 
blood than the foot. (Fig. 17.) 
The veins of the foot constitute a very intricate net-work of vessels. 
The veins of the frog, the sole, the lamin, the superficial and deep- 
seated coronary veins, unite to form coronary and plantar plexuses, 
(Fig. 15, “25,”) from which are formed plantar veins, (Fig. 15, “22,” 
25,”) which, by their union, constitute metacarpal and metatarsal veins, 
which lie anterior to, and by the side of, the plantar arteries. 
“Fic. 15.—Dissection of the horse’s foot. From Owen: 1, general integument, turned 
hack; 2, fatty mass, forming a cushion behind the great pastern ‘joint; 3, wall of hoof 
turned back, showing the vertically laminated processes projecting from its inner sur- 
face; 4, section of wall of hoof; 5, the articulation between the cannon and pastern 
bones; 6, 6, 6, aponeurotic tissues; 7,7, extensor tendon of the foot; 8, 9, 10, flexor 
tendons of the foot; 11, 12, 13, 14, 15, expansion of the great cartilage of the foot; 16, 
the coronary band raised from the hoof; 17, the vascular or sensitive hoof; 18, elastic 
eushion of the heels; 19, 20, 21, plantar artery; 22, 23, plantar veins; 25, part of cor- 
onary venous plexus raised from its position ; 26, 27, 28, plantar nerves. 
