The finer Anatomy of the Nervous System of Myxine glutinosa. 389 



The Seventh Nerve or the Facialis. 



Sanders (41) states that the Facialis in Myxine arises by one 

 root only, from the side of the Oblongata behind and below the 

 origin of the Trifacial. He describes the fibres as derived from the 

 anterior ganglion in several bundles, of which the more anterior 

 should pass through the anterior nucleus of larger cells and these 

 he »could not find the end of« but the posterior fasciculi >pass 

 obliquely backward and inward into that part of the latero- ventral^ 

 ganglion containing smaller cells lying behind the above-mentioned 

 clump of larger cells«. 



According to the description given by Ahlboen (2), the roots of 

 the Facialis in Myxine are very different to the same in Petromyzon. 

 The ganglion which the Facialis should spring from in Petromyzon 

 is situated in the dorsal wall of the Oblongata, above the Acusticus 

 nucleus. 



In the Teleostei we have got more knowledge of the anatomy 

 of the Facialis through the researches of ß. Haller (17). He finds 

 two roots, one upper sensory coming from the inner sensory region 

 and one motor. In Scyllium the roots are situated one above the 

 other and there is only one nerve, but in Salmo part of the motor 

 root is separated from the rest and pushed forwards, leaving the 

 Oblongata together with the posterior Trigeminus fascicles. The 

 other or posterior root contains mostly the sensory fibres. 



Van Gebuchten (14) finds that the Facial tract in Salmo is 

 somewhat similar to that in man and springs from large ramifying 

 cells whose ramifications mix with the descending root of the Trige- 

 minus. 



The Facialis is the most ventral of the metameric cranial nerves 

 and springs from the ventral and rostral part of the Corpora resti- 

 formia. In Myxine it is only a motor nerve and springs from two 

 cell nuclei situated one before the other in the rostral and ventral 

 part of the Corpora restiforraia. The part of the nerve which springs 

 from the most rostral of the nuclei leaves the brain at the most 

 frontal point, the part which springs from the more caudally situated 

 nucleus runs in a more lateral direction below the acustic ganglion. 

 The two nuclei are not entirely separated, some small cells connect- 

 ing them with each other. The cells of the rostral nucleus are larger 

 and of a somewhat different shape to those of the caudal one. The 

 lateral, part of the nerve issues from the brain more dorsally than 



