28 DISEASES OF THE HORSE'S FOOT 



where they form an arch between the deep flexor and the 

 suspensory ligament. From this arch (named the Sesa- 

 m old can) proceed the Metacarpal Veins. 



The Metacarpal Veins. — Three in number, they are 

 distinguished as an Internal and an External Metacarpal, 

 and a Deep or Interosseous Metacarpal. As we shall be 

 concerned with these in the higher operation of neurectomy, 

 we may give them brief mention. 



The Internal Metacarpal Vein, the largest of the 

 three, has relations with the internal metacarpal artery and 

 the internal plantar nerve. These relations were shortly 

 discussed under the section devoted to the arteries, to which 

 the reader may refer. 



The External Metacarpal Vein. — This ascends on the 

 external side of the flexor tendons in company with the 

 external plantar nerve. 



The Interosseous Vein. — This is an irregular vessel run- 

 ning up between the suspensory ligament and the posterior 

 face of the large metacarpal bone. 



F. THE NERVES. 



The Plantar Nerves.— These are two in number, and 

 are distinguished as Internal and External. 



The Internal Plantar Nerve lies behind and in close 

 contact with the great metacarpal artery during that vessel's 

 course down the region of the cannon. A point of interest 

 is that it gives off at about the middle of the cannon a 

 branch which bends obliquely downwards and behind the 

 flexor tendons to join its fellow of the opposite side — 

 namely, the external plantar. This it joins an inch or 

 more above the bottom of the splint bone. Measured in a 

 straight line, this is about 2\ inches below its point of 

 origin. Near the fetlock, at the level of the sesamoids, the 

 internal plantar nerve ends in several digital branches. 



The External Plantar Nerve. — This holds a position 

 to the outside of the metacarpal region, analogous to that 

 of the internal plantar nerve on the inside of the limb, 

 running down on the external edge of the flexor tendons. 



