DISSECTION OF THE HEAD AND NECK 307 



Observe also (1) the communication of Arnold's nerve 

 (ramus auricularis N. vagi] with the trunk of the N. facialis, a 

 little above the foramen stylomastoideum ; (2) a little branch, 

 inconstant, which sometimes runs to join the sympathetic plexus 

 upon the A. meningea media ; it is called the external superficial 

 petrosal nerve. 



Intermediate Nerve of Wrisberg (N. intermedius) (O. T. Sensory 

 Part of Facial Nerve). 



To this the geniculate ganglion belongs. Study 



(a) Larger superficial petrosal nerve (N. petrosus superficialis major). 



This carries sensory fibres from the N. intermedius by way of 

 the Vidian nerve to the sphenopalatine ganglion. 



(b) Cord of tympanum (chorda tympani). (Fig. 133.) 



This carries secretory fibres (sympathetic?) to the Gl. submaxil- 

 laris and Gl. sublingualis and taste fibres from the tongue to the 

 ganglion geniculi of the N. intermedius. Read carefully the com- 

 plicated course of the chorda tympani and follow it as well as 

 possible in the specimen and in models. 



Acoustic Nerve (N. acusticus) (O. T. Auditory Nerve). 



Note its position as regards the N. facialis in the meatus acus- 

 ticus internus. Observe that it is formed by the fusion of two 

 roots, one from the vestibule (radix vestibularis), the other 

 from the cochlea (radix cochlearis). The former root carries 

 sensory fibres from the vestibule and semicircular canals and 

 is concerned with the maintenance of equilibrium of the head and 

 eyes ; the latter root carries the impulses concerned in the sense 

 of hearing and in auditory reflexes. 



LARYNX. 



Examine the position and relations of the larynx. Note that 

 to its presence in the neck is due the laryngeal prominence, 

 or " Adam's apple" (prominentia laryngea, pomum Adami). 

 With a model of the larynx and the specimen before you, read 

 a general description of its construction before beginning the 

 dissection. 



Examine the relation of the larynx to the tongue. Study the 

 following : 



(a) Median glosso-epiglottic fold (plica glosso-epiglottica mediana} (0. 

 T. middle glosso-epiglottidean fold, or fraenum of the epiglottis). 



