488 THE ORGAN OF HEARING. 



a high columnar epithelium, but upon closer observation, it is seen 

 that the cellular elements are interspersed with fibers which extend 

 to the surface. Some investigators regard this tissue as fibrocar- 

 tilage ; others, again, as a tissue sui generis, consisting of epithelial 

 cells mingled with connective-tissue fibers. If the labium vestibulare 

 of the limbus spiralis be examined from the vestibular surface, a 

 number of irregular tubercles are seen at its inner portion (near 

 Reissner's membrane), while at its outer portion long, radially dis- 

 posed ridges may be observed, the so-called auditory teeth of 

 Huschke. The connective-tissue wall of the sulcus spiralis internus 

 consists of a nonnucleated fibrillar tissue which is continued into the 

 labium tympanicum. The latter is perforated by nerves, thus giving 

 rise at this point to the foramina nervosa. 



Between the point of attachment of Reissner's membrane and 

 the labium vestibulare, the superficial epithelium of the limbus spiralis 

 is flat, and lines the auditory teeth and the depressions between 

 them in a continuous layer. The epithelium of the sulcus spiralis 

 internus is somewhat higher. 



The ligamentum spirale forms the thickened periosteum of the 

 outer wall of the osseous cochlear canal. It presents two inwardly 

 projecting ridges, the crista basilaris, to which the membranous 

 lamina spiralis is attached, and the prominentia spiralis, which con- 

 tains one or several blood-vessels ; between the two ridges lies the 

 sulcus spiralis externus. The portion of the ligamentum spirale 

 forming the periosteum of the bony cochlear canal consists of a 

 fibrous tissue containing many nuclei, but changes internally into 

 a looser connective tissue. The connective tissue lying external to 

 the outer wall of the cochlear duct is very dense and rich in cellular 

 elements and blood-vessels, but in the crista basilaris it changes to 

 a hyaline, noncellular tissue, continuous with the lamina basilaris. 

 That portion of the spiral ligament lying between the prominentia 

 spiralis and the attachment of Reissner's membrane is known as 

 the stria vascularis. The epithelium covering this area (a portion of 

 the epithelium lining the cochlear duct) consists of columnar, darkly 

 granulated cells, which now and then are arranged so as to present 

 the appearance of a stratified epithelium, but which is more correctly 

 interpreted as an epithelium of the pseudostratified variety. This 

 epithelium shows no distinct demarcation from the underlying con- 

 nective tissue. Beneath this epithelium there is found a rich capil- 

 lary network, certain loops of which extend into the epithelium 

 (Retzius). It is thought that the stria vascularis is concerned in 

 the formation of the endolymph of the cochlear duct. 



The membranous lamina spiralis, or the basilar membrane, 

 extends from the tympanic lip of the osseous spiral lamina to the 

 crista basilaris of the ligamentum spirale. 



As already stated, the tissue composing the labium tympani- 

 cum of the limbus extends into the basilar membrane. In this 



