^544 A MANUAL OF ANATOMY 



which forms the cartilaginous bar of the first or mandibular arch. According 

 to some authorities, however, the incus is developed from the hyoid bar. 

 The stapes is developed from the dorsal part of the hyoid bar of the second 

 visceral arch, its foot-piece being derived from the labyrinth-cartilage withia 

 the fenestra ovalis. 



Ligaments of the Ossicles. — ^The synovial joints between the 

 malleus and incus and between the incus and stapes are provided 

 with thin capsular hgaments. The Hgaments which connect the 

 ossicles to the walls of the tympanic cavity are five in number, 

 three of them belonging to the malleus, one to the incus, and one 

 to the stapes. 



The ligaments of the malleus are anterior, posterior, and superior. 

 The anterior ligament is arranged in two parts, as follows: (i) the 

 band of Meckel (formerly known as the laxator tympani muscle), 

 which extends from the root of the long process to the fissure of 

 Glaser, through which it passes to be attached to the spine of the 

 sphenoid bone; and (2) the so-called anterior malleolar fold, which 

 extends from the short process to the anterior extremity of the 

 notch of Rivini. The posterior ligament extends from the short 

 process to the posterior extremity of the notch of Rivini. The 

 superior ligament extends from the head of the malleus to the roof 

 of the attic or epitympanic recess. 



The ligament of the incus connects the short process, near its 

 posterior extremity, to the fossa incudis. 



The annular ligament of the stapes connects the circumference 

 of the foot-piece, which is covered by cartilage, to the margin of 

 the fenestra ovalis, which is also covered by cartilage. 



Muscles of the Tympanum. — These are two in number, namely, 

 the tensor tympani and the stapedius. 



Tensor Tympani — Origin. — (i) The cartilaginous part of the 

 Eustachian tube, superiorly ; (2) the adjacent part of the great 

 wing of the sphenoid ; and (3) the wall of the osseous canal through 

 which the muscle passes. 



Insertion. — ^The inner aspect of the handle of the malleus, close 

 to its root. 



Nerve-supply. — A branch from the otic ganglion, and, through 

 it, from the internal pterygoid branch of the inferior maxillary 

 division of the fifth cranial nerve. 



The muscle consists of a fleshy belly, about \ inch long, and a 

 delicate tendon. In passing backwards to the tympanum it lies 

 in a canal, the entrance to which is situated within the petro- 

 squamous angle of the temporal bone. The canal is placed above 

 the osseous part of the Eustachian tube, from which it is separated 

 by the processus cochleariformis. On entering the tympanum the 

 tendon of the muscle bends sharply over the edge of the processus 

 cochleariformis, and then passes outwards to reach its insertion. 

 The tendon forms very nearly a right angle with the fleshy belly. 



Action. — To render tense the membrana t5anpani by drawing 



