678 



DISSECTION OF THE EAR. 



reach the inner wall of the tympanum. In this cavity the nerve supplies 

 filaments to the lining membrane and the fenestra rotunda ; and it termi- 

 nates in the three undermentioned branches, which are contained in 

 grooves on the promontory, and connect this nerve with others. 1 



Fig. 243. 



JACOBSON'S NERVE IN THE TYMPANUM (Breschet). 



a. Carotid artery. 



6. Tensor tympani muscle. 



c. Inferior maxillary trunk of the fifth nerve. 



d. Otic ganglion. 



Nerves : 



1. Petrous ganglion of the glosso-pharyn- 

 geal. 



2. Nerve of Jacobson. 



3. Sympathetic ou the carotid. 



4. Small superficial petrosal nerve. 



5. Offset to join large petrosal nerve. 



6. Branch to Enstachian tube. 



7. Facial nerve ; 8, chorda tympani branch. 

 9. Nerve of the otic ganglion to the tensor 



muscle. 



Branches. One branch is arched forwards and downwards, and enters 

 the carotid canal to communicate with the sympathetic ( 3 ) on the artery 

 (p. 116). 



A second ( 5 ) is directed upwards to join the large superficial petrosal 

 nerve in the hiatus Fallopii. 



And the third ( 4 ) has the following course : It ascends in front of the 

 fenestra ovalis, and near the gangliform enlargement on the facial nerve, 

 to which it is connected by filaments (fig. 35). Beyond the union with 

 the facial, the nerve is named small superficial petrosal, and is continued 

 forwards through the substance of the temporal bone, to end in the otic 

 ganglion (p. 144). 



Nerves to muscles. The tensor tympani muscle is supplied by a branch 

 from the otic ganglion (fig. 243, 9 ) : the stapedius receives an offset from 

 the facial trunk ; and the laxator tympani from the chorda tympani nerve (?). 



1 Instead of viewing these filaments as offsets of the nerve of Jacobson they 

 may be supposed to come from the other nerves : according to this view the tym- 

 panic plexus would be derived from several sources. 



