THE LUMB0-8ACSAL PLEXUS. 777 



large number and their shortness. Those of the deep layer are supplied by 

 filaments from a single long and thick branch, which descends between the 

 pertoratus and the internal gastrocnemius. It may be remarked, that the 

 hlament going to the so-called small plantar muscle, passes underneath the 

 external gastrocnemius, outside the perforatus, and that, by its position it 

 exactly represents the soleus ramuscule of Man. We are. therefore with 

 Vicq-d Azyr, Cuvier, and others, justified in naming this little muscle the 

 solearis (soleus), instead of continuing to designate it the small plantaris 

 wJiich appellation is given to another muscular element. 



6. In its course along the tendo-AchiUis, the sciatic nerve emits some 

 slender cutaneous filaments, which we do not consider worthy of further 

 notice. 



TERMINAL BRANCHES. 



Plantae Neeves (Fig. 355, 10, 12).— These two nerves enter the 

 tersal sheath, behind the perforans tendon, along with the plantar arteries. 

 Towards the superior extremity of the cannon, they definitively separate 

 from each other; the external is carried outwards between the precited 

 tendon and the rudimentary metatarsal bone ; the internal is placed with 

 that tendon, and follows the posterior border of the inner metatarsal bone. 

 Both afterwards descend on the fetlock, where they comport themselves 

 like the analogous nerves of the anterior limb. 



DIFFERENTIAL CHARACTEES IN THE LUMEO-SAOliAL PLEXUS OP OTHER THAN SOLIPED 



ANIMALS. 



As was the case with the brachial plexus, so with this ; the differences observed 

 being trifling in the upper pari of the limb, but more numerous and important in the 

 region of the foot, the complexity of arrangement varying with the species. 



Ruminants.— The lumbo-sacral plexus of these animals is constituted by two lumbar 

 and three sacral nerves, as in Solipeds; but the third sacral onlv gives a very fine 

 iilament, which readies the second in passing downward and forward. 



At the femoro-tibial articulation, the branches of the plexus are similar to those in 

 the Horse. Below that articulation, the following disposition lias been observed in 

 the Slieejp. 



The mufculo-cutaneous branch of the popliteal is long and thick. It descends on the 

 anterior face of the metatarsus, and at the metatarso-phalangeal ariiculatinn bifurcates, 

 the branches forming the dorsal collaterals of the digits. The anterior tibial nerve 

 prf sents two branches parallel to the tibial vessels ; one passes aloug the metatarsal 

 region, and when it arrives at the bottom of the groove between tl:e condyles of the 

 metatarsus, it divides into two branches that constitute the di-ep collaterals of the 

 dij;its ; these collaterals furnish filaments to the posterior face of the digilal region. 



The great sciatic resembles that of Solipeds. Its terminal brandies, or plantar 

 nerves, dilfer from those of the Horse in the absence of the transverse anastomosis that 

 unites the two cords in the region of the tendons. 



Pig. — The lumbo-sacral plexus of this animal is composed of two lumbar and three 

 sac.val nerves ■ reckoning, of course, as a sacral nerve, the trunk that escapes from 

 between the last lumbar vertebra and the sacrum. The plexus may be divided into 

 two portions, the first furnishing a femoral and an obturator nerve. The internal 

 saphenous branch of the femoral nerve is long and voluminous; at its origin it is as 

 large as the branch passing to the anterior muscles of the thigh, and it descends on the 

 inner face of the metatarsus, forming the dorsal collateral of the internal digit. 



The great snatie is voluminous and round. Tlie branches it gives to the museles 

 of the pelvis and femur are disposed nearly as in Solipeds and Euminants; but 

 differences are observed in the external popliteal and the terminal branches. 



The musculo cutaneous nerve reaches the metatarsal region, where it separates into 

 three branches, which form the doj-s-il collaterals of the digits. 



The anterior tibial neroe descends between the two principal metatarsals, ard at the 

 root of the middle digits divides to anastomose with the plantar nerves. Of th se tiie 

 external is small, and gives collaterals to the two external digits,- the internal, the 



