GENERAL MORPHOLOGY OF THE NERVOUS SYSTEM. 



21 



roots, the more dorsal connected with the lobus lineae lateralis 

 and the more ventral connected with the tuberculum acusticum, 

 which together supply the lateral line organs of the head. In bony 

 fishes and aquatic amphibia only the more ventral root is present. 

 In terrestrial vertebrates the roots which supply lateral line organs 

 on both the trunk and head disappear because the sense organs 

 are useful only in aquatic life. Of this group of nerves only the 

 auditory remains in higher vertebrates. The nerves which 

 supply the lateral line organs of the head enter into close relations 



R. ophthal. superfic 



Supraorbital 

 canal 



Hyomand. 

 canal 



Infraorbital canal 



Lateral line . 

 canal 



R. hyomandibularis 



FIG. 6. A diagram of the lateral line canals and pit organs together with the 

 nerves which supply them in a ganoid fish (Amia caVvd). After E. Phelps Allis. 

 The canals are shaded with cross lines and the canal organs are shown as black 

 discs in the course of the canals. The pit organs are shown as rows of black dots. 

 Only the peripheral nerve trunks are shown, the ganglia and roots being omitted. 



with the facialis or trigeminus nerve and their rami have been 

 variously named as rami of the latter nerves. Three chief rami 

 are formed, a supraorbital, an infraorbital and a mandibular, 

 which will be more fully described in a later chapter (see Chap. 

 VII). 



Ventrad or ventro-cephalad from the auditory root are the two 

 roots, a sensory and a motor, which constitute the seventh cranial 

 or jacialis nerve. The two roots enter a ganglion from which 



