362 



STRUCTURE OF THE EAR. 



Fig. 1S3. 



External, middle, and internal ear. 



#, tympanic cavity, containing the bones ; 



c, hammer and its three muscles, viz., 



d, internal muscle, lodged in the thick- 

 ness of the superior wall of Eustachian 

 tube, and bending at a right angle to be 

 inserted in superior part of handle of 

 hammer ; e, anterior muscle of 'hammer; 

 jf, external muscle of hammer ; g, inte- 

 rior half of membrana tympani, holding 

 the handle of the hammer ; A, tube of 

 Eustachius ; i, internal ear or labyrinth. 



Tympanic cavity. 



TYMPANIC CAVITY, ITS BONES, MUSCLES, AND NERVES. 



Pig. 184 : , hammer, holding, by the anterior and superior part of its 



handle, and by its round extremity, #, the 

 membrana tympani ; <?, internal muscle of 

 hammer ; d, stirrup upon fenestra ovalis ; 

 0, muscle of stirrup ; 1, facial nerve, com- 

 municating with, 2, great superficial pe- 

 trosal, and, 3, little superficial petrosal ; 

 4, chorda tympani ; 5, 5, nervous twig of 

 internal muscle of hammer, arising from 

 motor portion of fifth pair, and traversing otic ganglion ; 6, nervous twig, 

 arising from facial and going to muscle of stirrup ; 7, ganglion of Gasser. 



DIAGRAM SHOWING THE FACIAL IN THE AQUEDUCT OF FALLOPIUS AND ITS ANASTOMOSES. 



Fig. 185 : 1, facial ; 2, nerve of Wrisberg ; 3, petrosal twig of vidian 

 Fig. 185. nerve ; 4, ganglion of Meckel ; 5, little 



petrosal of Longet ; 6, twig of muscle of 

 stirrup; 7, auricular twig of Arnold ; 8, 

 chorda tympani, cut ; 9, ganglion of An- 

 dersch ; 10, nerve of Jacobson, divided 

 into six twigs, viz., 11, twig anastomos- 

 ing with, 12, carotid plexus, 13, twig 

 anastomosing with great superficial pe- 

 Faciai in the aqueduct of Faiiopius. trosal (little deep petrosal of Arnold), 14, 

 little superficial of Arnold, uniting with little petrosal of Longet to form 

 15, a common trunk, which goes to 16, otic ganglion ; 17, twig of fenes- 

 tra rotunda ; 18, twig of fenestra ovalis ; 19, twig of tube of Eustachius. 

 The explanation usually given of the functions of these various parts 

 Common hy- is as follows : The waves of sound, moving through the at- 

 functSn of the Biosphere, pass down the exterior canal and strike upon the 

 auditory parts, membrane of the drum, which is thrown into vibration there- 



