LITERARY NOTICES. 



Spino-occipital Nerves.^ 



The term spino-occipital nerves was applied in 1895 by Max 

 Fiirbringer to certain nerves of the selachians which have been known 

 since the time of Stannius to occupy a more or less ambiguous posi- 

 tion between the vagus and the first spinal nerves. The net result of 

 the present investigation is to substantiate the last expressed opinion 

 of Gegenbaur, that these nerves belong not with the vagus, but with 

 the spinals, and that their relations with the vagus are in all cases 

 secondary. This group of nerves is further subdivided into * 'occipi- 

 tal nerves," which have lost their spinal character and have become 

 incorporated into the head, and ''occipto-spinal nerves," whose eman- 

 cipation from the spinal nerves is not yet complete, a distinction of 

 degree only and not resting on any profound morphological basis. 

 Peripherally these nerves unite with each other and with more or less 

 of the succeeding spinal nerves to form a plexus which divides into a 

 caudal brachial plexus for the fin and a cervical plexus for the pre- 

 zonal somatic musculature. This plexus crosses the vagus and may 

 be more or less mt-imately bound up with it, but does not form a 

 true anastomosis with the vagus. 



The importance of this region for the proper understanding of the 

 problems of cephalogenesis can hardly be over-estimated. It is in the 

 selachians that this series of transitional nerves is most highly devel- 

 oped and, accordingly, it is here that Dr. Fiirbringer has done his 

 chief work ; nevertheless this exhaustive study has been supplemented 

 by a personal examination of representatives of all of the other verte- 

 brate classes and by a thorough mastery of the literature of all of the 

 vertebrates. The thoroughness with which this latter work was done 

 is indicated by the fact that the bibliography contains 560 titles and 

 the text gives evidence that all of them were consulted. 



As an illustration of the complexity of the conditions, we may 

 cite the case of Hexanchus, where portions of the skull which origi- 



^Dr. Max Fiirbringer. Ueber die Spino-occipitalen Nerven der Selachier 

 und Holocephalen und ihre vergleicbende Morphologic. Festschrift f. Gegen- 

 baur, III, pp. 351-788, 8 plates, Leipzig, 1897. 



