TYMPANIC OSSICLES 



205 



the fluid of the internal ear. The Malleus, or hammer, is about 

 18-19 mm. long, and has an average weight of 23 mgms. It 

 consists of a thickened rounded head and a long handle the 

 manubrium, which is attached to the tympanic membrane, the tip 

 of the handle reaching the umbilicus. Near the insertion of the 

 head and handle rises a bony process the processus gracilis or 

 processus Folianus, which projects forward and is continued by a 

 ligament, the anterior ligament by means of which the hammer is 

 anchored to the wall of the tympanum. There is also a shorter 

 protuberance, the processus brevis, which presses against the edge 

 of the upper surface of the drum. Three other ligaments are 

 attached to the malleus, the external ligament, binding it to the 



SUPERIOR. LIGAMENT OF MALLEUS 

 V 



BOD 1 ' OF INCUS 



SHORT PROCESS e, 

 POSTERIOR LIGAMENT 

 OF INCUS 



LONG PROCESS OF INCUS 



PYRAMIDALI5 



TO WHICH THE TENDON OF 

 M ST.1PLDIUS 15 ATTACHED 



ANTERIOR LIGAMENT OF MALLEU5 



^ _^^?M. TEN5PR TYMPANl 



SEPTUM CANALIS 

 ' '. ^r~MUSCULOTUBARII 



MANUBRIUM MALLE.I 



FIG. 44. Diagram of the left Membrana Tyrapani and Chain of Tympanic Ossicles 

 seen from the medial aspect. 



The line A B is the axis of rotation of the malleus and incus. The dotted line 

 represents the line of leverage applied from the handle of the malleus to the posterior 

 ligament of the incus. The stapes lies almost at right angles to the plane of the 

 paper. 



external face of the tympanic cavity, the superior or suspensory 

 ligament, attaching the top of the head to the roof of the cavity, 

 and the posterior ligament. These ligaments prevent the malleus 

 from rotating in any other axis than a horizontal one whose line 

 passes through the head of the malleus and the anterior ligament 

 (Fig. 44). The posterior surface of the head of the hammer fits 

 into the saddle-like hollow in the anterior surface of the body of the 

 anvil-bone or incus. This is a larger bone than the malleus, weigh- 

 ing on the average 25 mgms. The body of the incus is drawn 

 out on its posterior side to a process the short process, which 

 is attached by a ligament to the posterior wall of the tympanic 

 cavity, forming one end of the malleo-incal axis mentioned above. 

 Almost at right angles to the short process, the inferior surface of 



