32 LABORATORY OUTLINE OF NEUROLOGY 



sense that they contain functionally different components. 

 These components may come from roots of several different 

 nerves by anastomoses peripherally of the ganglia. Some of the 

 more important peripheral nerves of the dogfish are as follows: 



(1) The supra-orbital trunk, containing the r. ophthalmicus 

 superficialis V (general cutaneous) for the skin of the top of the 

 head, and lateral line fibers for supra-orbital lateral line organs 

 (the r. ophthalmicus superficialis VII); (2) r. ophthalmicus 

 profundus V (general cutaneous), passing through the middle 

 of the orbit, beyond which it anastomoses with the r. ophthal- 

 micus superficialis V to supply the skin of the snout (the 

 superficial and deep ophthalmic branches of the V nerve to- 

 gether correspond approximately with the ophthalmic branch 

 of the human trigeminus); (3) the infra-orbital trunk, passing 

 across the floor of the orbit, below which it divides into the r. 

 buccalis VII (lateralis) for infra-orbital lateral line organs, r. 

 maxillaris V (general cutaneous) for the skin of the upper jaw, 

 and r. mandibularis V (general cutaneous and motor) for the 

 skin and muscles of the lower jaw; (4) r. palatinus VII (visceral 

 sensory) for the mucous membrane and taste-buds of the roof 

 of the mouth (represented by the great superficial petrosal nerve 

 of the human body) ; (5) the hyomandibular trunk, passing be- 

 hind the spiracular cleft to the region of the hyoid arch and 

 lower jaw, containing the r. mandibularis internus VII (visceral 

 sensory) for taste-buds and mucous membrane lining the lower 

 jaw, motor VII fibers for muscles of the hyoid arch (r. hyoideus), 

 and lateral line fibers for hyomandibular lateral line organs (r. 

 mandibularis externus VII). The visceral sensory and motor 

 fibers correspond with the facial trunk of the human body. 



The components of these peripheral nerves can be com- 

 pletely separated only by microscopic methods, though a skilful 

 dissector can separate the lateralis components of many of the 

 nerves (see Ewart, '93 and Norris, '18). The nerve com- 

 ponents of vertebrates are fully described by Johnston ('06 

 and '09). 



20. The gills are visceral structures. Their sensory nerves 

 terminate centrally in the visceral sensory column of the medulla 

 oblongata, and their motor nerves arise from the visceral motor 

 column (see Sections 15 and 23). Each gill cleft has a branchial 



