Organ of Hearing. 233 



Malleus 



317. The Ossicula auditus, 318. The Tympanic 



from the outside. Magn. = 3. Cavity and Ossicula auditus, 



from above. 



b) The Incus or anvil has a body, a short and a long pro- 

 cess. The short process is articulated with the posterior wall of the 

 tympanum by means of ligamentous fibres; the long process is bent 

 inwards at its extremity and terminates in a rounded projection, the lenti- 

 cular process or Ossiculum lenticulare Sylvii. With the latter the head 

 of the stapes articulates. 



c) The stapes or stirrup consists of a head, from which 

 diverge the two curved c r u r a ; these are connected at their extremities 

 by the base, which fits into the Fenestra ovalis, and the space between 

 them is filled out by a membrane, the Membrana propria stapedis. 



The muscles which move the Ossicula auditus are : the M. ten- 

 sor tympani, which heightens the tension of the Membrana tympani, 

 and arises from the Eustachian tube and under surface of the petrous 

 bone ; it lies in the Semicanalis, its tendon bends around the Rostrum coch- 

 leare, and is inserted into the neck of the malleus. - - M. laxator tympani, 

 which relaxes the Membrana tympani, arises from the spinous process 

 of the sphenoid bone, and, passing through the Grlaserian fissure is inserted 

 into the long process of the malleus. - - M. stapedius, the muscle of 

 the stirrup (Fig. 314) lies in the hollow of the Eminentia pyramidalis ; 

 its tendon emerges from the orifice at the apex of the pyramid, and is 

 inserted into the head of the stapes. 



Heitzmann, Atlas. I. 30 



