THE MIDDLE EAK 



613 



ery inward to the manubrium mallei, and an inner circular layer 

 whose thickest portions are found close to the manubrium and near 

 the periphery of the membrane ; between these points the circular 

 layer of fibres is par- 

 tially or entirely de- 

 ficient. Just within 

 the fibro-cartilagmous 

 ring at the periphery 

 of the membrane the 

 circular layer of fibres 

 abruptly ends. 



The cutaneous lay- 

 er of the tympanic 

 membrane forms a 

 very thin coat, its epi- 

 dermis consisting of a 

 Malpighian layer one 

 or two cells deep, 

 which is covered by 

 several flattened non- 

 nucleated cells of the 

 horny portion. The 

 derma or corium is 

 very thin, contains no 

 papillae, and is inti- 

 mately adherent to the 

 fibrous layers of the 

 membrane; it con tains 

 neither glands nor 

 hairs. 



The mucous layer 

 of the tympanic mem- 

 brane is even thinner 

 than the cutaneous. 

 It consists of a flat- 

 tened epithelium 

 which rests almost di- 

 rectly upon the layer 

 of circular fibres. A few connective tissue fibres pass irregularly 

 from the mucous, through the fibrous, to the cutaneous layer, thus 

 firmly uniting the several layers into a compact membrane. 



FIG. 446. SECTION THROUGH THE MARGIN OF THE 



TYMPANIC MEMBRANE OF A CHILD. 

 a, fibro-cartilaginous ring ; &, bone ; c, derma of the 

 external auditory canal ; d, tympanic mucosa ; e, ', 

 epidermis ; /, radial fibres, and /*, circular fibres of the 

 tympanic membrane ; 0, muco&a of the membrane ; ft, 

 epithelium of the tympanum ; , blood vessels, x 55. 

 (After Kolliker.) 



