394 J«bn F. Holm 



ally of the lower root of the fifth nerve (Fig. 19). The motor origin 

 is found in a nucleus which is situated very close to the Vagus 

 nucleus but somewhat anteriorly of it. It is doubtless an independent 

 ganglion, as the cells are not only of different form to those of the 

 Vagus ganglion, but their staining properties as regards Iron-haema- 

 toxylin are quite different and while the cells of the former stain 

 gray, those of the latter are found to be nearly quite black. 



The Nervus lateralis-glossopharyngeus may be considered as an 

 independent metameric cranial nerve; where the portion which corre- 

 sponds to the Lateralis is the sensory nerve, that of the Glosso- 

 pharyngeus corresponds to the motor nerve. In more highly organised 

 fishes the Glossopharyngeus differentiates itself from the Lateralis 

 and becomes an independent nerve, as, for instance, described by 

 Haller (17) in Salmo, or by Allis (3) in Amia calva, where the 

 Glossopharyngeus receives some of the sensory fibres of the Late- 

 ralis. 



In the higher evolution of animal life and where animals lose 

 the organs of the lateral line, the Nervus lateralis vanishes while 

 the Glossopharyngeus remains. 



The Tenth Nerve or Nervus Vagus. 



The Nervus vagus has been seen by all authors who have oc- 

 cupied themselves with the brain anatomy ofMyxine. Sanders (41) 

 finds that in Myxine the Vagus has one root only, which is divided 

 into three bundles emerging from the extreme posterior end of the 

 latero-ventral ganglion. From the dorsal side of the same ganglion 

 there arises a very small root which he thinks may be looked upon 

 as a dorsal root of the Vagus. G. Retzius (38) has come to the 

 same conclusion vis-a-vis the Vagus as Sanders. FtJRBRiNGER (12) 

 believes that the Vagus nerve has from one to four roots, generally 

 one; the other dorsal nerve with ganglion he calls the first spine- 

 occipital nerve. The sensory Vagus (as I call the upper root of the 

 Vagus) on entering the brain divides into two branches in the same 

 manner as the sensory elements in the Lateralis-glossopharyngeus 

 as previously described. One branch turns straight rostrally and 

 ends in a nucleus of small gray matter situated a little rostrally to 

 the nerve entrance; the other one runs straight into the brain, where 

 part of its fibres end amongst some gray matter situated about half 

 way between the surface of the brain and the central gray. The 



