BONES OF THE TYMPANUM. 



509 



The Malleus (hammer) consists of a head, neck, handle (manu- 

 brium), and two processes, long (procesaus gractiis), and short (processus 

 brevis). The manubrium is connected to the membrana tympani by 

 its whole length extending to below the central point of that mem- 

 brane. It lies beneath its mucous layer, and serves as a point of 

 attachment to which the radiating fibres of the fibrous layer converge. 

 The long process descends to a groove near the fissura Glaseri, and 

 gives attachment to the laxator tympani muscle. Into the short pro- 

 cess is inserted the tendon of the tensor tympani, and the head of the 

 bone articulates with the incus. 



Fig. 156.* 



* A diagram of the ear. p. The pinna, t. The tympanum. /. The labyrinth. 

 1. The upper part of the helix. 2. The antihelix. 3. The tragus. 4. The 

 antitragus. 5. The lobulus. 6. The concha. 7. The upper part of the fossa 

 innominata 8. The meatus. 9. The membrana tympani, divided by the sec- 

 tion. 10- The three little bones, crossing the area of the tympanum, malleus, 

 incus, and stapes ; the foot of the stapes blocks up the fenestra ovalis upon the 

 inner wall of the tympanum. 1 1 . The promontory. 12. The fenestra rotunda ; 

 the dark opening above the ossicula leads into the mastoid cells. 13. The Eus- 

 tachian tube ; the little canal upon this tube contains the tensor tympani mus- 

 cle in its passage to the tympanum. 14. The vestibule. 15. The three semi- 

 circular canals, horizontal, perpendicular and oblique. 16. The ampullae 

 upon the perpendicular and horizontal canals. 17. The cochlea. 18. A de- 

 pression between the convexities of the two tubuli which communicate with the 

 tympanum and vestibule ; the one is the scala tympani, terminating at 12 ; the 

 other is the scala vestibuli. 



