DISSECTION OF THE ANTERIOR LIMB. 29 



downwards and forwards from the homy spur behind the fetlock, 

 becoming attached within the wing of the os pedis. A knowledge of 

 these relationships is of importance for the performance of the lower 

 operation of neurotomy. The collateral branches of the digital 

 arteries are : — 



1. At different levels numerous small branches for the skin, tendons, 

 or articvilations. Among these may be included the rameaux echelcmnes 

 of Bouley (Plate 10). These branches, some of them of considerable 

 size, spring from the posterior aspect of the artery, and anastomose 

 across the back of the digit with corresponding branches from the oppo- 

 site side, forming arches arranged like the steps of a ladder. 



2. The Perx)endicular Artery^ Avhich comes off at a right angle about 

 the middle of the first phalanx, and divides almost immediately into an 

 ascending and a descending set of bi-anches, both of which are distri- 

 buted on the front of the first phalanx. Branches from each of these 

 sets anastomose with corresponding vessels from the opposite side. 



3. The Artery of the Plantar Cushion. 



4. Vessels forming the Coronary Circle. 



The last two, as well as the terminal branches of the digital arteries, 

 will be described in connection with the foot. 



The Small Metacarpal Artery (Plate 9). This, the smaller 

 terminal branch of the posterior radial artery, descends behind the 

 knee and towards its inner side. It is superficially placed to the 

 fibrous band completing the carpal arch, while the large metacarpal 

 lies beneath that structure. In company with it is the first part of the 

 median vein. At the level of the head of the inner metacarpal bone it 

 crosses to the outer side by passing between the suspensory ligament 

 and the subcarpal ligament, or check -band furnished from the 

 back of the carpus to the tendon of the deep flexor. It here anasto- 

 moses Avith a branch already described as descending from the supra- 

 carpal arch. In this way the subcarpal arch is formed. 



The Subcarpal or Deep Palmar Arch gives off the following two 

 pairs of arteries : — 



1. The Anterior or Dorsal Interosseous Metacarpal Arteries. — These 

 are small vessels (Plate 9), one on each side of the limb, which turn 

 forward round the heads of the small metacarpal bones, and descend in 

 the grooves between these bones and the large metacarpal. They 

 supply the skin and subjacent structures on the front of the metacarpus, 

 and anastomose above the fetlock with divisions of the artery springing 

 from the large metacarpal at its point of bifurcation. 



2. The Posterior or Palmar Interosseous Metacarpal Arteries. — These 

 descend on the edge of the suspensory ligament, each being internally 

 placed to the small metacarpal bone of its own side. They anastomose 

 like the preceding, and supply small branches to the suspensory ligament 



