THE EAR 



presents a marked differentiation of the epithelial lining, which is 

 there raised in the form of a prominent crescentic fold, falsely 

 termed by the older anatomists the crista acustica, from its sup- 

 posed connection with the auditory function. Like the maculae of 

 the saccule and utricle, the cristae are supplied by the vestibular 

 nerve and are concerned with the function of equilibration. 



The cristae are clothed with tall columnar cells which, though 

 somewhat taller, are otherwise similar in structure to those of the 

 maculae, and are similarly divisible into sustentacular cells and hair 

 cells. They are also covered by a gelatinous cuticular formation, 

 containing otoliths, which is here known as the cupola. 



THE COCHLEA 



The cochlea, like the vestibular portion of the internal ear, con- 

 sists of a bony case which incloses a series of spiral membranous 

 canals. 



The bony cochlea possesses a peculiar pyramidal shape. The 

 base of the pyramid is in contact with the anterior aspect of the 



vestibule ; its apex or cupola 

 is directed forward, outward, 

 and slightly downward. The 

 pyramid is hollow and contains 

 in its axis a conical bony 

 support, the modiolus, which 

 tapers from a broad base to 

 a pointed apex beneath the 

 broader, blunt, and rounded 

 cupola of the outer bony wall. 

 The modiolus contains a broad 

 canal which receives the coch- 

 lear division of the eighth 

 cranial nerve as it enters from 

 the internal meatus. 

 The outer surface of the modiolus supports a bony shelf, the 

 lamina spiralis, which winds in a spiral manner from its base to 

 its apex, and ends in a hook -like process, the liamulus. This shelf 

 only partially spans the interval between the modiolus and the 

 outer wall of the cochlea. In life the remaining interval is com- 

 pleted by a firm fibrous membrane, the basal membrane (lamina 

 lasilaris). Thus the cylindrical canal of the cochlea, which is 

 wound spirally around the modiolus making two and one-half turns 



FIG. 455. AXIAL SECTION THROUGH THE 



COCHLEA OF A FETAL CALF. 

 a, internal auditory meatus in which is 

 the cut end of the cochlear nerve as it enters 

 the modiolus. x 6. (After Kolliker.) 



