600 THE CHORDA TYMPANI AND TASTE. 



passes into the facial or Fallopian canal. At first it has a transverse direction as far as the 

 hiatus of this canal ; it then bends at an acute angle at the "knee" (a) above the tympanic 

 cavity, to descend in an osseous canal in the posterior wall of this space (fig. 429). It emerges 

 from 'the stylo-mastoid foramen, pierces the parotid gland, and is distributed in a fan-shaped 

 manner (pes anserinus major). [The superficial origin is at the lower margin of the pons, in 

 the depression between the olivary body and the restiform body, as indicated in fig. 428, 

 Vila.] 



Its branches are: 1. The motor large superficial petrosal (J). It arises 

 from the " knee " or geniculate ganglion within the Fallopian canal, in the cavity 

 of the skull, runs upon the anterior surface of the temporal bone, traverses the 

 foramen lacerum medium on the under surface of the base of the skull, and passes 

 through the Vidian canal to reach the sphenopalatine ganglion (p. 595). It is 

 uncertain whether this nerve conveys sensory branches from the second division of 

 the trigeminus to the facial. 



2. Connecting branches (/?) pass from the geniculate ganglion to the otic ganglion. 

 For their course and function, see Otic yanglion (p. 597). 



3. The motor branch to the stapedius muscle (y). 



4. The chorda tympani (i i) arises from the facial before it emerges at the 

 stylomastoid foramen (*), runs through the tympanic cavity (above the tendon of 

 the tensor tympani, between the handle of the malleus and the long process of 

 the incus), passes out of the skull through the petro-tympanic fissure, and then 

 joins the lingual nerve at an acute angle (p. 596, 4). Before it unites with this 

 nerve, it exchanges fibres with the otic ganglion (m). Thus, sensory fibres can 

 enter the chorda from the third division of the trigeminus, which may run 

 centripetally to the facial to be distributed along with it. In the same way, sensory 

 fibres may pass from the lingual nerve through the chorda into the facial (Longet). 

 .Stimulation of the chorda which even in man may be done in cases where the 

 tympanic membrane is destroyed causes a prickling feeling in the anterior margins 

 and tip of the tongue (Troltsch). O. Wolfe found that the section of the chorda in 

 man abolished the sensibility for tactile and thermal stimuli upon the tip of the 

 tongue ; and the same was true of the sense of taste in this region. It is supposed 

 by Calori, that these fibres enter the facial nerve at its periphery (especially through 

 the auriculotemporal into the branches of the facial), that they run in a centripetal 

 direction in the facial, and afterwards pursue a centrifugal course in the chorda. 

 [It is possible that sensory fibres pass from the spheno-palatine ganglion of the 

 fifth through the Vidian nerve and large superficial petrosal to enter the facial. 

 These fibres may be those that appear in the seventh as the chorda fibres which 

 administer to taste. Bigelow asserts that the chorda tympani is not a branch of the 

 facial, but the continuation of the nervus intermedius of Wrisberg.] The chorda 

 also contains secretory and vaso-dilator fibres for the sub-maxillary and sub-lingual 

 glands ( 145). 



Gustatory Fibres. The chorda also contains fibres administering to the sense of 

 taste, for the margin and tip of the tongue (anterior two-thirds), which are conveyed 

 to the tongue along the course of the lingual. Urbantschitsch made observations 

 upon a man whose chorda was freely exposed, and in whom its stimulation in the 

 tympanic cavity caused a sensation of taste (and also of touch) in the margins and 

 tip of the tongue. 



It would seem, therefore, that the gustatory fibres of the chorda have their 

 origin in the glossopharyngeal nerve. They may reach the chorda: 1. Through 

 the portio intermedia of Wrisberg, as already mentioned. 



2. There is a channel beyond the stylomastoid foramen, viz., through the ramus communicans 

 cum glosso-pharyngeo (fig. 429), which passes from the last mentioned nerve in that branch of 

 the facial which contains the motor fibres for the stylohyoid and posterior belly of the digastric 

 muscle (Henle's N. styloideus). This nerve also supplies muscular sensibility to the stylohyoid 

 and posterior belly of the digastric muscles. It is also assumed that, by means of these anasto- 

 moses, motor fibres are supplied by the facial to the glossopharyngeal nerve. 3. A union of the 



