452 NERVOUS SYSTEM. 



nues to adhere closely to it, almost to the styloid foramen ; it 

 then abandons the facial nerve at a very acute angle, and run- 

 ning upwards and forwards, gets into the cavity of the tympa- 

 num, on a level with, but a line or two exterior to the pyramid. 

 It then crosses the tympanum nearly horizontally, between the 

 long crus of the incus and the handle of the malleus, adhe-ring 

 to the latter so as to be affected by its vibrations. At the fore 

 part of the tympanum, it anastomoses with some other filaments 

 of the fifth pair, by which its, size is augmented, but it gives no 

 branches to the parts contained in the tympanum. It then is- 

 sues from the latter cavity through the glenoid foramen, and 

 descending a short but somewhat variable distance along the 

 ramus of the lower jaw, terminates by anastomosing at an acute 

 angle with the lingual branch of the trigeminus. 



To Mr. John Hunter is due the merit of having traced the 

 continuity and identity of the Vidian nerve with the chorda 

 tympani. The continental European anatomists, for the most 

 part, seem ignorant of his observations, and give a very differ- 

 ent account of the matter. Some consider it to arise from the 

 facial at its angle, and to anastomose at the other end with the 

 pterygoid, or the reverse; and they very generally agree in re- 

 garding the chorda tympani as a filament from the facial, just 

 before the latter gets out of the stylo-rnastoid foramen. 



The Vidian Nerve, or Superficial Petrous, also traverses the 

 tympanum in another place. Just below the posterior extre- 

 mity of the Eustachian Canal, there is a small foramen, which 

 leads upwards to the superior surface of the petrous bone, and 

 downwards to a small gutter upon the promontory: this gutter 

 is converted into a canal that opens upon the under surface of 

 the petrous bone, between the carotid canal and the jugular 

 fossa. Through the course indicated, passes a filament from 

 the superficial petrous nerve: tins filament is joined by another 

 detached from the sympathetic while in the carotid canal, and 

 the two communicate at the base of the cranium with the gang- 

 lion of the glosso-pharyngeal nerve.* These filaments were 

 discovered by Professor J,icobson, of Copenhagen, and form 

 what is now called the Anastomosis of Jacobson. 

 -t 



* Meckel, Man. D'Anat. vol. iii. p. 174. Jacobson, Supplem. Act. Hafn. 

 vol. v. p. 292. An. 1818. 



