146 THE SALAMANDER 



R. aheolaris (r.al.) (communis) 



R. mandibularis internus . . .... Hoffmann. 



At the point where this branch is given off, von Plessen and Rabi- 

 nowicz, Hoffmann and Driiner report a few scattered clusters of 

 ganglion cells, but they are only detectable by microscopic means. 

 Von Plessen and Rabinowicz call them the buccal ganglion. Driiner 

 is convinced that they do not represent the remains of the ganglion 

 laterale VII (connected with the lateral line system), and also finds 

 fine sympathetic fibres entering the nerve in this region. Hoffmann 

 goes further and suggests that the ganglion may be the forerunner 

 of the otic ganglion of mammals. Certain it is that it exists and that it 

 has a connexion with the sympathetic system. 



The alveolar nerve turns a little antero-laterally, and, keeping ven- 

 tral to the quadrate and pterygoid, passes to the mesial side of the 

 lower jaw. At about the level of the processus coronoideus it pene- 

 trates a foramen in the pre-articular (fo.i.den; Fig. 7) and comes 

 to lie between this bone and Meckel's cartilage — that is, on the 

 mesial side of the latter. The nerve then passes anteriorly through 

 the alveolar canal and emerges from it, anterior to the pre-articular, 

 between the edges of the dentary. Its ultimate branches are distri- 

 buted to the epithelium of the mouth-floor, between the M. genio- 

 glossus and the mandible. Within the jaw it anastomoses several 

 times with the internal mandibular branch of the Vth nerve as above 

 noticed, but as a whole these two nerves are separated from one 

 another by Meckel's cartilage. 



Homology of Chorda tympani. 



A very great deal has been written on, and around, this subject, 

 and the conclusions drawn therefrom have been widely different. 

 Only the briefest resume of the discussion may be given here. 



The chorda tympani is typically a mammalian nerve, and receives 

 its name from its relations in the human subject, where it appears to 

 pass through the middle ear, or tympanum, across the dorsal edge 

 of the tympanic membrane. Actually the nerve is outside the tym- 

 panum altogether, morphologically speaking, since it is covered by 

 the mucous lining of the cavity. After receiving fibres from the otic 

 ganglion it joins the lingual nerve — a branch of the Vth nerve — and 

 with it enters the inferior dental canal of the lower jaw. 



Now the chorda tympani is a branch of the facial nerve, which 

 in turn is a visceral nerve related to the spiracle or its homologue. 

 Hence the question arises whether, if a nerve corresponding to the 



