THE EXTERNAL EAR. 



477 



is thickened, forming the so-called ciiticular ridge, which possesses 

 papillae and is supplied with vessels and nerves. 



The lamina propria ends peripherally in a thickened ring of fibro- 

 elastic tissue, the annulus fibrosus, which unites at the sulcus tym- 

 panicus with the periosteum of the latter. The lamina propria is 

 composed of connective-tissue fibers, in which two layers may be 

 distinguished externally, the radiate fibers, the stratum radiatum, 

 and internally, the circular fibers, the stratum circulare. The exter- 

 nal radiate layer extends from the annulus to the umbo and manu- 

 brium, and is interrupted in the flaccid portion of the tympanic 



Pinna. 



Fig. 366. Schematic representation of the complete auditory apparatus (Schwalbe). 



membrane by the upper fourth of the manubrium and the short 

 process of the malleus ; it gradually thins out toward the center 

 until it finally disappears in the vicinity of the umbo. The fibers 

 of the inner (circular) layer are circularly disposed. This layer is 

 thickest at the periphery of the tympanic membrane, becoming 

 gradually thinner toward the lower end of the manubrium, where 

 it disappears. Between the two layers of the lamina propria is a 

 small quantity of loose connective tissue. The manubrium of the 

 malleus is inclosed within the tympanic membrane. This is due to 

 the union of the fibers of the radial layer with the outer strata of 

 the manubrial perichondrium, the handle of the malleus being here 

 covered by a thin layer of cartilage. In the posterior upper quad- 

 rant of the tympanic membrane the two layers of the lamina propria 



