CHAP. iv.J HEARING. 1323 



the Fallopian canal carrying the seventh or facial nerve (Fig. 166 

 VII.) is a protuberance marking the position of the swollen ends 



FIG. 168. FRONTAL (TRANSVERSE VERTICAL) SECTION THROUGH THE TYMPANUM. 



(LEFT EAR.) (Schwalbe.) 



The figure, partly diagrammatic, is magnified twice, and shews the front part of the 

 tympanum as seen from behind ; the incus has been removed, the articular 

 surface on the head of the malleus being indicated. 



mt. The membraua tympani. mf. membrana flaccida. nibr. handle of the malleus. 

 p. b. short process of the malleus. 



Ig. e. external ligament, Ig.s. the superior ligament of the malleus. 



TT. The bony projection from which the tendon of the tensor tympani passes to 

 the malleus, f.o. the fenestra ovalis. v. the front part of the vestibule, c. the 

 beginning of the first (basal) turn of the cochlea. 



or ampullae of two of the semicircular canals, namely those known 

 as the horizontal and superior. 



The distance across the tympanum between the beginning of 

 the chain of ossicles at the point of the handle of the malleus 

 and its end at the fenestra ovalis is very short, much shorter 

 than the length of the chain itself; the greater part of the chain, 

 including the bodies and processes of, that is to say nearly the whole 

 of, the malleus and incus, owing to the peculiar form and articu- 

 lation of the ossicles, lies above a line drawn from the point of the 

 handle of the malleus to the fenestra ovalis. Cf. Figs. 167, 168. 

 We must now turn to the details of the manner in which the 

 ossicles are attached to the membrana tympani, to each other, and 

 to the fenestra ovalis. 



813. The membrana tympani (Fig. 169) irregularly elliptical 

 in form with the long axis vertical is placed obliquely (Figs. 162, 

 168 m. t.}, at the inner end of the external meatus. Nearly 

 the whole of the circumference of the membrane is fixed in 

 a groove of the ring-shaped bone, the annulus tympanicus. At 

 the extreme top the ring is wanting ; and the portion of the 

 membrane thus attached, not to the ring but to the bone 

 above, being less tense than the rest of the membrane, and indeed 

 thrown into folds, is distinguished as the membrana ftaccida 



