196 THE GENERAL ANATOMY OF GORILLA [SECT. A 



The study of the peripheral nervous system of the Gorilla falls 

 naturally into two divisions. 



(A) In the first place, a certain number of differences have 

 been noted between the dispositions found in the Gorilla and in 

 Man respectively, the differences affecting the course or connections 

 of such nerves as are given in the following list (taken from 

 Eisler's work 1 ). 



The facial nerve is more complicated in the Gorilla than in the Chim- 

 panzee, but less so than in the Orang-utan and in Man : its communications 

 with the external carotid plexus are richer than in Man. 



The ramus descendens hypoglossi contributes to the innervation of the 

 sternomastoid muscle. The ansa hypoglossi receives branches from the first 

 two cervical nerves. The great auricular and the superficial cervical nerves 

 come from the second cervical only, the supra-clavicular from the second, 

 third and fourth cervical nerves. The phrenic nerve contains sympathetic 

 fibres. The nerve to the M. subclavius is not a distinct entity, since it arises 

 from the uppermost (external) anterior thoracic nerve. The medial cuta- 

 neous nerve is derived principally from the first thoracic and intercosto- 

 humeral branch of the second thoracic nerves. The musculo-cutaneous nerve 

 receives no contribution from C. vn. ; it supplies the M. coraco-brachialis, 

 but does not perforate it. The deep volar branch of the ulnar nerve springs 

 from a communication between the ulnar and median nerves, and passes 

 beneath the ligamentum carpi volare proprium to enter the hand. The 

 median nerve passes beneath the M. pronator teres. The radial nerve does 

 not perforate the M. supinator brevis. 



The ilio-hypogastric and ilio-inguinal nerves arise from the thirteenth 

 thoracic nerve, which is accordingly considered by Eisler as representative of 

 the first lumbar nerve of Man. The femoral nerve receives most of its 

 muscular fibres from L. iv. The anterior tibial (deep peroneal) nerve 

 supplies (in correlation with the shifting fibula-wards of the dorsal inter- 

 osseous muscles) the opposed surfaces of the second and third toes. 



No contributions to the sciatic portion of the sacral plexus come from 

 nerves posterior to the second sacral. The pudendal plexus is formed by the 

 second and third sacral nerves, the coccygeal plexus by S. iv. and S. v. 



(B) A second line of enquiry raises the question as to the 

 relation of the general position of the limb-plexuses (as regards 

 the spinal cord and its segments) in the Gorilla and other types. 

 Here the first point to notice is that in one feature at least the 

 Simiidae stand together with the Hominidae in contrast to all 

 other Primates (save certain Senmopitheci). The feature thus 



1 Das Gefiiss- und periphere Nervemystem des Gorilla. Exhaustive descriptions 

 have been published also by 15olk, Kohlbrugge and Sperino. 



