THE NERVOUS SYSTEM OF THE PIG 



723 



The spinal nerves number on each side eight in the cervical region, fourteen 

 (commonly) in the thoracic, seven in the lumbar, and four in the sacral. Some 

 of the special features of the nerves of the limbs are as follows: 



The brachial plexus is derived from the same nerves as in the ox, l^ut the root 

 furnished l)y the sixth cervical is relatively smaller. The plexus consists of two 

 parts, the upper of which emerges above the scalenus, the lower between the two 

 parts of that muscle. The more important differences in the nerves emanating 

 from the plexus from the arrangement in the ox occur in the lower part of the limb. 

 The cutaneous branch of the radial nerve divides at the carpus into branches which 

 concur with the dorsal branch of the ulnar nerve in supplj'ing the dorsal digital 

 nerves, two for each digit. The volar digital nerves, also two for each digit, are 

 formed by the terminal branches of the median nerve and the volar or deep branch 



Deep peronea 

 nerve 



Super ficia 

 peroneal nerve 



Internal 

 saphenous 



nerve 



Tibial nerve _ — 



Internal plantar 

 nerve 



Fig. 537. — Nerves of Distal Part of Right Hind Fig. 5.38. — Nerves of Distal Part op Right Hind 



Limb of Pig, Anterior View (Schematic). Limb of Pig, Posterior View (Schematic). 



p, Dorsal proper digital nerves. p. Plantar proper digital nerves. 



of the ulnar nerve. The formation and arrangement of the digital nerves are 

 indicated in the annexed schematic figures. 



The lumbo-sacral plexus is derived from the ventral branches of the last three 

 lumbar and first sacral nerves. The distribution of the branches of the ]:)lexus 

 differs chiefly in the distal part of the limb. The superficial peroneal nerve is 

 large and terminates ])y forming the greater part of the dorsal digital nerves. 

 The latter, two for each digit, are also in part formed by the terminal branches of 

 the deep peroneal nerve. 



The tibial nerve divides at the tarsus into internal and external plantar nerves. 

 The latter divide to form the plantar digital nerves, two for each digit. In addi- 

 tion, the external plantar nerve sujiplies a branch to the dorsal aspect of the outer 

 (fifth) digit. The arrangement of the digital nerves is indicated by the annexed 

 schematic figures. 



