

of the membrane. Branched or dendritic fibers, as pointed out by Griiber, are also present, 

 especially in the posterior half of the membrane. 



Vessels and Nerves. The arteries of the tympanic membrane are derived from the deep 

 auricular branch of the internal maxillary, which ramifies beneath the cutaneous stratum; and 

 from the stylomastoid branch of the posterior auricular, and tympanic branch of the internal 

 maxillary, which are distributed on the mucous surface. The superficial veins open into the 

 external jugular; those on the deep surface drain partly into the transverse sinus and veins of 

 the dura mater, and partly into a plexus on the auditory tube. The membrane receives its 

 chief nerve supply from the auriculotemporal branch of the mandibular; the auricular branch of 

 the vagus, and the tympanic branch of the glossopharyngeal also supply it. 1 



SUPERIOR LIGAMENT 

 OF MALLEOLUS 



EPITYMPANIC 

 RECESS 



NECK OF 

 MALLEUS\ 



ANTERIOR LIGAMENT 



AND ANTERIOR 



PROCESS OF 



MALLEOLUS 



INSERTION 



OF TENSOR 



TYMPANI 



MUSCLE, 



ARTICULAR SURFACE 

 FOR BODY OF INCUS 



FLACCID PORTION OF 

 MEMBRANA TYMPANI 



|||!j POSTERIOR 



TYMPANIC 

 SPINE 



TYMPANIC 

 ORIFICE 

 OF CANAL 

 FOR CHORD,. 

 TYMPANi 

 NERVE 



EUSTACHIAN 

 TUBE 



TENSE PORTION OF 

 MEMBRANA TYMPANI 



FIG. 912. The right membrana tympani with the hammer and the chorda tympani, viewed from within, from behind, 



and from above. (Spalteholz.) 



The Labyrinthic or Medial Wall (paries labyrinihica; inner wall) (Fig. 913) is 

 vertical in direction, and presents for examination the fenestrse vestibuli and 

 cochleae, the promontory, and the prominence of the facial canal. 



The fenestra vestibuli (fenestra ovalis) is a reniform opening leading from the 

 tympanic cavity into the vestibule of the internal ear; its long diameter is horizontal, 

 and its convex border is upward. In the recent state it is occupied by the base of 

 the stapes, the circumference of which is fixed by the annular ligament to the margin 

 of the foramen. 



The fenestra cochleae (fenestra rotunda) is situated below and a little behind the 

 fenestra vestibuli, from which it is separated by a rounded elevation, the promontory. 

 It is placed at the bottom of a funnel-shaped depression and, in the macerated bone, 

 leads into the cochlea of the internal ear; in the fresh state it is closed by a mem- 

 brane, the secondary tympanic membrane, which is concave toward the tympanic 

 cavity, convex toward the cochlea. This membrane consists of three layers: an 



1 Wilson, J. G.. American Journal of Anatomy, 1911, xi. 



