256 



extra-petrous, would serve as a practical basis for clinical descriptions, 

 and would give to the sensory mechanism of this nerve the importance 

 which it deserves. 



That the facial nerve stands in close sensory relationship to the 

 structures of the auditory mechanism is not surprising, when one con- 

 siders that it is a branchial nerve, and throughout the whole course of 

 phylogenic development is related to the first branchial cleft and its 

 adjacent visceral arches, more especially the posterior or the hyoid arch. 

 From this cleft and adjacent arches are developed the structures of 

 the middle and external ear. 



Another developmental factor bearing on the close relationship of 

 this nerve to the auditory mechanism is found in its relationship to 

 the auditory ganglia, from which are developed the cochlear and vesti- 

 bular divisions of the auditory nerve. The acoustic ganglia and the 

 geniculate are derived primarily from the neural ridge, and in the 

 earlier stages of embryonic life are grouped together into a common 

 ganglionic mass, the ganglion acousticum-faciale. And it is only in the 

 later stages of embryonic life that the}^ become differentiated into the 

 geniculate, from which are derived the fibres of the sensory root of 

 the facial, the ganglion spirale which gives rise to the fibres of the 

 cochlear nerve, and the ganglion of Scarpa, which gives rise to the 

 fibres of the vestibular nerve. So that both in the development of the 

 neural, as well as in the other structures of the auditory mechanism, 

 embryological investigations have shown a most intimate relationship 

 between the facial nerve and the internal, middle and external ear. 

 That the sensory function of the facial nerve in its relationship to the 

 auditory mechanism has escaped detection is to be ascribed to the very 

 complex and intricate anatomy of this region. The trigeminus, glosso- 

 pharyngeal, vagus and the upper cervical nerves all converge and ana- 

 ßtomose in the ear cleft. I would, however, particularly emphasise the 

 fact that the facial nerve plays a central and important part in the 

 innervation of this region. 



The following chapters: Sensory symptoms and syndromes; Neur- 

 algic affections of the facial nerve (Otalgia) ; Posterior poliomyelitis of 

 the geniculate ganglion ; The sensory mechanism of the facial nerve as 

 a reflex factor in the production of facial spasms and twitchings; 

 Sensory symptoms occurring in the course of facial neuritis, are of 

 great physiological and practical interest but they have nothing to do 

 with this anatomical journal. 



In conclusion, the author expresses his belief that the sensory sym- 

 ptomology of the 7th cranial nerve deserves an established place in the 

 nomenclature, and that this sensory system, although small in area, is 

 of great importance because of its relation to the highly developed and 

 very sensitive auditory mechanism. 



Abgeschlossen am 1. April 1910, 



Frommannsche Buchdmckerei (Hermann Fohle) in Jena. 



