42 THE ANATOMY OF THE HORSE. 



The Artery of the Plantar Cushion arises from the digital, just as 

 that vessel passes within the upper border of the lateral cartilage, and 

 it passes obliquely downwards and backwards to its destination. Besides 

 supplying the plantar cushion, it gives off a branch which turns forwards 

 to concur in the formation of the circumflex artery of the coronary 

 cushion. 



The Coronary Circle. Where each digital artery lies under cover 

 of the lateral cartilage, it gives off an anterior and a posterior branch 

 which inosculate on the middle line before and behind with the corre- 

 sponding branches of the opposite side, and thus form an arterial circle. 

 This circle closely embraces the os coronae ; and among the largest 

 branches furnished by it are two which emanate from its anterior half, 

 and descend, one at each border of the extensor tendon, to aid in form- 

 ing the circumflex artery of the coronary cushion. 



The Circumflex Artery of the Coronary Cushion (Chauveau). 

 This is a slender vascular arch placed immediately above the coronary 

 cushion, to which its branches are distributed. It is fed in front by 

 the two above-mentioned vessels from the coronary circle, and behind, 

 on each side, by the before-mentioned branch from the artery of the 

 plantar cushion. 



The Preplantar Artery is the smaller of the two terminal branches 

 of the digital. It passes forwards through the notch in the wing of the 

 os pedis, and then along the preplantar groove on the laminal surface of 

 that bone, where its branches are expended in the sensitive laminse. 



The Plantar Artery passes along the plantar groove to enter the 

 foramen of the same name. Within the os pedis it inosculates with the 

 corresponding vessel of the opposite side, forming the plantar arch, or 

 semilunar anastomosis. From this intra-osseous arch, a great number of 

 branches proceed. An ascending (anterior laminal) set of these leave 

 the os pedis by the numerous small foramina which cribble its laminal 

 surface. A descending (inferior communicating) set escape from the 

 bone by the series of large foramina which open on the sharp edge 

 separating its laminal and plantar surfaces. These inferior communi- 

 cating arteries anastomose right and left with each otfrer, and thus form 

 the circumflex artery of the toe. From the concavity of this artery 

 branches pass backwards, and supply the tissue of the sole. 



The Veins of the Foot. — Intra-osseous Vessels. Within the os pedis 

 the arterial branches are accompanied by satellite veins. There is 

 thus a semilunar venous anastomosis, to which small veins converge 

 from the laminal surface of the bone. The blood from this sinus is 

 drained away by a larger vessel which passes out by the plantar fora- 

 men in company with the plantar artery, and joins the posterior part of 

 the coronary plexus. Extra-osseous vessels. The foot is richly provided 

 with a superficial system of vessels, which are arranged in the form of a 



