234 Journal of Comparative Neurology. 



Fiirbringer ('97, Plate VIII, Figs. 5 and 6) in Esox and 

 Mullus. 



In another specimen from the one just described and 

 figured the composition of the r. cervicalis is somewhat 

 different. In addition to sensory and motor fibres from 

 the first spinal nerve b, it receives also a large number of 

 sensory fibres from the ramus ventralis c. The latter 

 nerve has a larger proportion of fine fibres than in the 

 specimen figured and it is not improbable that the fibres 

 which it gives to the r. cervicalis are derived from the 

 dorsal root b. In this specimen, as in the other, the 

 motor fibres of the r. cervicalis clearly all come from the 

 motor root b. 



V. — Comparative Review of the First Spinal Nerve. 



The cervical nerve corresponds to the cervical, i. e., pre- 

 zonal, plexus of the Selachii and in part to the n. hypo- 

 glossus of the higher vertebrates. Of course in the latter 

 case the sensory element here present will have to be ex- 

 cluded. The results of Harrison ('95) go to show that the 

 sterno-hyoid muscle of the salmon has the same origin 

 ontogenetically as the tongue-muscles of the higher forms, 

 that is, it is a true somatic muscle, derived from the lateral 

 muscle plates. The nerve supply is therefore unquestion- 

 ably homologous. Nevertheless the r. cervicalis of the 

 bony fish cannot be homologized without reserve with 

 either the cervical plexus of the Selachii or the hypo- 

 glossus of higher forms, for in both of these cases the 

 nerves in question supply not only the post-hyal, but also 

 the pre-hyal ventral musculature, while in the bony fish 

 the latter is, as we shall see, absent. These points are 

 again referred to in our account of the m. genio-hyoideus. 

 Section 7, IV, 5, iv.' For further critical and historical 



