THE TYMPANUM. 217 



Processus Cochleariformis, the small end of the septum tubae, projecting 



into the tympanum. (See p. 17.) 



POSTERIOR WALL, separates it from the mastoid cells, and presents the 

 Openings of the Mastoid CeXs. Ridge of the Aqueductiis Fallopii, curving 

 downwards and nearly vertically. (See above.) 



Describe the Ossicles of the Tympanum. They are three small bones, 

 which form a chain across the tympanic cavity, connecting the membrana 

 ympani with the fenestra ovalis, and named the 



Malleus, or Hammer, A consists of a head, neck, short process, .ong pro- 

 cess, or Processus Gracilis, and handle, or Manubrium. The short pro- 

 cess and handle are fastened to the middle layer of the drumhead. The 

 long process is received into the Glaserian fissure, and the head articulates 

 with the head of the Incus. 



Incus, or Anvil,B has a head, also a long and a short process. The head 

 articulates with the head of the malleus, the 

 short process with the posterior wall of the 

 tympanum, the long process with the head of 

 the stapes, by the Os Orbiculare, its convex ex- 

 tremity. 



Stages, or Stirrup, C presents a head, neck, base 

 and crura. Its head articulates with the incus, 

 its base rests on the membrane closing the 

 fenestra ovalis, its neck receives the tendon of 

 the stapedius muscle. 



Name the Ligaments of the Ossicles. They are the 

 Ligamentum Mallei Anterius, from the spina tympanica major to the neck 



and long process of the malleus. 

 Lig. Mallei Externum, from the border of the Rivinian segment (p. 214), 



to the neck of the malleus. Its posterior fibres are the 

 Lig. Mallei Posticum, (Laxator tympani minor muscle of Sommering) is 



simply the posterior group of fibres of the preceding ligament. 

 Lig. Mallei Superius, (Suspensory Kg. of the malleus) from the roof of the 



tympanum to the head of the malleus. 

 Lig. Incudis Superius, from the roof of the tympanum to the head of the 



incus (Arnold). 

 Lig. Incudis Posticum, from the posterior wall of the tympanum to the short 



process of the incus. 

 Lig. Obturatorium Stapedium, a thin membrane which closes the opening 



between the crura of the stapes. 



