25S ANIMAL PHYSIOLOGY. 



Posteriorly, the tympanum communicates with the mastoid 

 cells, a set of small irregular spaces in the mastoid part of 

 the temporal bone, which can scarcely be supposed to be 

 functionally important, as they vary greatly in extent, and 

 have little development in young persons. 



On the inner side, the tympanum is bounded by the petrous 

 part of the temporal bone, which contains the internal ear 

 imbedded in it; and here there are two small openings, one 

 above the other, which are important as establishing a com- 

 munication between the middle and internal ear. The lower 

 of these openings, the fenestra, rotunda, about the size of a 

 pin head, is blocked up with a membrane, the secondary 

 membrana tympani; while the upper opening, the fenestra 

 ovalis, somewhat larger, has fitted into it the base of the 

 stapes, one of the small tympanic ossicles. 



191. The tympanic ossicles, three in number, the malleus, 

 incus, and stapes, make a communication between the niern- 

 brana tympani and the internal ear. The ossicles termed 

 malleus and incus, from a fancied resemblance to a hammer 

 and anvil, lie one in front of the other, the malleus foremost. 

 The malleus has at its upper part a head, which articulates 

 behind with the incus; and descending from the head is the 

 handle, or manubrium, the extremity of which we have 

 already seen to be connected with the membrana tympani. 

 Another process, procesxus gracilis, springs from below the 

 head of the malleus, and passes forwards to be attached in a 

 fissure of the temporal bone. The incus articulates by its 

 thickest part with the malleus, and sends out two processes, 

 one of which projects horizontally backwards, and has a 

 ligamentous attachment in front of the mastoid cells, while 

 the other, which is longer, descends vertically, and is turned 



this country and on the continent. In such a work as this it is sufficient 

 to mention two objections to that idea; namely, that'it is anatomically 

 impossible, and that I have myself, as elsewhere recorded, actually 

 seen through a perforation in the palate, the extremity of the Eusta- 

 chian tube lying open when the throat was at rest, and closed in the 

 act of swallowing. And it is to be remembered that it is only about 

 the extremity of the tube that there can be a question; since no one 

 doubts the patency of the osseous part, and Kiidmger has demon- 

 strated a permanently patent canal in the first part of the cartilagin- 

 ous portion, 



