880 



THE NERVES. 



Fig. 475. 



the phalanges, giving to that muscle and the flexor of the metatarsus short, but 

 thick, ramuscules. It descends to the front of the tarsus, always covered by the 

 anterior extensor of the phalanges, and placed at the external side of the anterior 

 tibial vessels. When it arrives below the tibia, it lies immediately alongside the 

 pedal artery, and follows it, in its metatarsal portion, to near the fetlock. It 



then separates from its satellite vessel — and 

 passes on the side of the digit, where it ends 

 in cutaneous filaments (Fig. 375, 5). 



Among the ramuscules this nerve gives 

 off in its course, are cited those to the pedal 

 muscle. 



2. Branches of the Muscles of the 

 Deep Pelvi-crural Kegion. —This region 

 comprises the obturator internus, gemelli, 

 and quadratus femoris muscles. The nerve 

 sent to them is long and attenuated ; it is 

 detached from the sciatic nerve at the middle 

 of the supra-cotyloid ridge, and descends 

 with that trunk behind the coxo-femoral 

 articulation, to distribute its terminal di- 

 visions to the above-named muscles. The 

 longest and thickest of these goes to the 

 quadratus femoris. That passing to the 

 obturator internus re-enters the pelvic cavity 

 by the small sacro-sciatic notch, and ascends 

 to the vicinity of the ilio-sacral articulation. 



3. Branch to the Ischio-tibial, or 

 Posterior Crural Muscles. — This branch 

 is thick and short. It arises from the bend 

 formed by the great femoro-popHteal nerve 

 at the gemelli muscles, and soon divides 

 into several ramifications which are distri-' 

 buted to the short portion of the biceps, the 

 middle and inferior parts of the semitendi- 

 nosus, and into the semimembranosus. Some 

 of the filaments for the latter muscle pass 

 between it and the adductor magnus, in 

 which they partly terminate (Fig. 474, 12). 



4. External Saphenic Nerve. — This 

 branch commences at from 2 to 6 inches 

 from the point where the great sciatic nerve 

 dips between the two portions of the gastroc- 

 nemius muscle. It is placed on the external 

 portion, and descends beneath the special 

 aponeurotic layer covering that muscle, to 



the origin of the tendon of the hock. It then receives its accessory nerve — the 

 reinforcing filament which comes from the cutaneous branch of the small femoro- 

 popliteal nerve, and is prolonged beneath the tibial aponeurosis into the channel of 

 the hock, accompanying the external saphenic vein, and following the external 

 border of the fibrous band that goes to strengthen the tendo-Achillis. In this 



EXTERNAL NERVES OF THE POSTERIOR 



LIMH. 



1,2, Great sciatic nerve; 3, external saphenic 

 nerve; 4, externul popliteal nerve; 5, 

 anterior tibial nerve; 6, musculo-cuta- 

 neoiis nerve; 7, origin of the peroneal- 

 cutaneous branch ; 8, accessory branch 

 of the external saphenic nerve; 9, ex- 

 ternal plantar nerve with its divisions, 

 which cover the digital artery and vein. 



