I 



Basis stapedis 



DISSECTION OF THE HEAD AND NECK 391 



(h) Fixing- muscle of the base of the stapes (M. fixator baseos sta- 



pedis). 



Muscles of Auditory Bones. 



These muscles (musculi ossiculorum auditus) are two in 

 number : 



(a) Tensor muscle of tympanum (M. tensor tympani). 



(b) Stapedius muscle (M. stapedius). 



Study form, position, origin, insertion, action, and innerva- 

 tion of each. 



FIG. 193. 



Capitulum mallei, ^^^^^^ 



'St" ^Ak Crus breve 



Spina tympanica minor -| WJft f Incudis 



Processus anterior <Folii)-J8C ^A ^P lo " gum ' 



Processus laterali 



Insertio M. tensor tympani 

 Manubrium mallei 



The cavum tympani with the membrana tympani and the ossicula auditus. Only that part of the 

 cavum tympani supporting the membrana tympaiii is represented. ( From Gegenbaur, Lehrb. der Anat. 

 des Mensch., Leipzig, 1899, 7 Aufl., Bd. ii. p. 615, Fig. 728.) 



The student should next review certain structures previously 

 studied, viz, the chorda tympani (see p. 264 and Figs. Ill and 

 115), the plexus tympanicus and the N. tympanicus (see p. 271), 

 and the tuba auditiva [Eustachii] (see pp. 293 and 296). 



The study of the internal ear is very difficult. Much can be 

 learned by fastening a temporal bone in a vice and chiselling 

 cautiously until the osseous labyrinth is exposed. The temporal 

 bone of a new-born babe or of a younger foetus will be found 

 very helpful for study. The labyrinth of a guinea-pig and an 

 embryo pig will also well repay study. In the museum, the ex- 

 quisite preparations of isolated labyrinths, Wood's metal corro- 

 sions, and models are available for study. The student should 

 use these and should study his atlases and good descriptive 

 texts in connection with them. 



Osseous Labyrinth (Labyrinthus osseus). 



Here the student should study successively the vestibule (ves- 

 tibulum), the snail-like body (cochlea), and the internal acoustic 

 meatus (meatus acusticus internus). 



