354 NERVOUS SYSTEM. 



way, it leaves the parent nerve and crosses obliquely beliind the 

 flexor brachii, passing between that muscle and the coraco-hume- 

 ralis, to both of which it sends filaments ; it then winds forward 

 and re-appears upon the upper and fore part of the arm, where 

 it becomes subcutaneous, ramifying upon the faschia, and pro- 

 longing its ramifications over the knee upon the metacarpus. 

 2. A small slip detached opposite to the elbow-joint, distributed 

 to the heads of the flexor muscles. 3. In its course down the 

 arm, several small twigs to the flexor muscles, 4. Above the 

 knee, a communicating slip separates, which obliquely crosses 

 over the fleshy terminations of the flexors, and joins the ulnar 

 nerve as it passes the joint. 



The ulnar nerve, which, at its origin from the plexus, 

 holds a middle situation between the radial and the nerve before 

 described — the spiral — also accompanies for a short distance the 

 humeral artery. In its course to the elbow it preserves the line 

 of the OS humeri ; there it runs over the inner and back part of 

 the joint, glides down the arm concealed by the posterior borders 

 of the flexores metacarpi, inclines a little inward before the ten- 

 don of the flexor medius to reach the back of the knee, where it 

 is found under the posterior annular ligament, within a dense 

 faschial sheath, creeping along close to the inner edge of the 

 trapezium. From this, it gains the border of the tendo perforans, 

 and becomes the external metacarpal nerve. Its branches are — 

 1 Soon after its origin, one that may be called the internal cu- 

 taneous nerve, which runs over the elbow-joint and ramifies in the 

 loose cellular substance about the inward part of the olecranon. 

 2. Three or four considerable branches which penetrate the heads 

 of the flexors, also destined to the joint. 3. A little above the 

 knee comes off" a branch which pierces the faschia and becomes 

 subcutaneous. After having detached some twigs to the back 

 part of the knee, this nerve runs along the outer and posterior 

 part of the cannon to the fetlock, where it disperses its ramifica- 

 tions. 4. A short but considerable branch to the back of the 

 knee, sending twigs into the joint. 5. A branch is sent oflf im- 

 mediately below the knee, which turns suddenly forward and 

 disperses its ramifications in front of the leg. 



The metacarpal nerves, iw^er/?o/ and external, conimne 

 down the leg along the borders of the flexor tendons, over the 

 fetlock-joint, where they become the plantar nerves ; these pursue 

 their course, behind their corresponding bloodvessels, to the 

 posterior part of the foot, which they penetrate to the inner sides 

 of the lateral cartilages. About midway between the knee and 

 fetlock, the internal nerve sends a branch obliquely over the 

 flexor tendons, which joins the external nerve : with this excep- 



