TOPOGRAPHICAL ANATOMY OF THE EAR. 163 



ers the ossicles and those portions of the muscles and tendons 

 which pass through the tympanum. On the floor and on the 

 anterior, inner, and posterior walls, the epithelium is of the 

 conoidal, ciliated variety. On the promontory, roof, ossicles, 

 and muscles, the cells are of the pavement variety and not 

 ciliated, the transition from one form to the other being grad- 

 ual. The entire membrane contains numerous lymphatics, a 

 plexus of nerve-fibres and nerve-cells, with some peculiar 

 cells, the physiology of which is not understood. The pres- 

 ence of mucous glands in the tympanic cavity, indicated by 

 Troltsch 1 and others, has been denied by Kessel, for the 

 human subject, though he has found them in the cat and 

 dog. 2 



We have thus given a general sketch of the physiological 

 anatomy of the middle ear, and shall not find it necessary to 

 treat more fully of the cavity of the tympanum, the mastoid 

 cells, or the Eustachian tube, except as regards certain points 

 in their physiology. The minute anatomy of the membrana 

 tympani and the articulations of the ossicles can be more con- 

 veniently considered in connection with the physiology of 

 these parts. 



General Arrangement of the Bony Labyrinth. The in- 

 ternal portion of the auditory apparatus is contained in the 

 petrous portion of the temporal bone. It consists of an ir- 

 regular cavity, called the vestibule, the three semicircular 

 canals (13, 14, 15, Fig. 10), and the cochlea (16, Fig. 10). 

 The general arrangement of these parts in situ and their re- 

 lations to the adjacent structures are shown in Fig. 10. Fig. 

 13, showing the bony labyrinth isolated, is taken from the 

 beautiful photograph contained in Riidinger's atlas. 



The vestibule is the central chamber of the labyrinth, 



1 TROLTSCH, Diseases of the Ear, New York, 1869, p. 174 ; and, Anatomic de 

 Vortille, Bruxelles, 1863, p. 94. 



2 KESSEL, in STRICKER, Manual of Human arid Comparative Histology, The 

 New Sydenham Society, London, 1873, vol. iii., p. 58. 



