

THE INTERNAL EAR OR LABYRINTH 



1055 



sulcus spiralis externus. The upper portion of the spiral ligament contains numerous 

 capillary loops and small bloodvessels, and is termed the stria vascularis. 



The osseous spiral lamina consists of two plates of bone, and between these are 

 the canals for the transmission of the filaments of the acoustic nerve. On the upper 

 plate of that part of the lamina which is outside the vestibular membrane, the perios- 

 teum is thickened to form the limbus laminae spiralis (Fig. 929), this ends externally 



FIG. 928. Diagrammatic longitudinal section of the cochlea. 



in a concavity, the sulcus spiralis internus, which represents, on section, the form 

 of the letter C; the upper part, formed by the overhanging extremity of the limbus, 

 is named the vestibular lip; the lower part, prolonged and tapering, is called the 

 tympanic lip, and is perforated by numerous foramina for the passage of the cochlear 

 nerves. The upper surface of the vestibular lip is intersected at right angles by a 

 number of furrows, between which are numerous elevations; these present the 

 appearance of teeth along the free surface and margin of the lip, and have been 



Fibres of Cochlear division 

 Of Auditory nerve 



Crista a&ilaris 



FIG. 929. Floor of ductus cochlearis. 



named by Huschke the auditory teeth (Fig. 930). The limbus is covered by a layer 

 of what appears to be squamous epithelium, but the deeper parts of the cells with 

 their contained nuclei occupy the intervals between the elevations and between the 

 auditory teeth. This layer of epithelium is continuous on the one hand with that 

 lining the sulcus spiralis internus, and on the other with that covering the under 

 surface of the vestibular membrane. 





