148 THE AUDITORY NERVE AND COCHLEA, BY W. WALDEYER. 



just as on the other side they pass without interruption into 

 the tympanal epithelium of Reissner's membrane (figs. 321 

 and 324). They are deficient on the external borders of the 

 teeth, as well as on the apices of the processes of the crista. 

 The membrana tectoria here rests (see below, and figs. 321 and 

 322, M f) immediately upon the osteogenous substance of the 

 crista, but at both these points a few flattened cell rudiments 

 are sometimes met with. Towards the angle of attachment of 

 the membrane of Reissner, the epithelial rows separated by 

 the teeth and processes constantly run together to form a 

 continuous layer (fig. 324, e and <?,). Independently of the 

 immediate connection of the cells in question with the re- 

 maining epithelium of the ductus, to which Mr. Baer (Student 

 in Medicine) has called attention in the lettering of the pre- 

 paration, the history of its development clearly demonstrates 

 the correctness of what has been above stated, since in em- 

 bryoes the ductus everywhere possesses a continuous epithelial 

 investment, which only undergoes apparent interruption in. 

 consequence of the great development of the osteogenous sub- 

 stance of the crista, just as the investment of the membrana 

 tectoria is apparently interrupted, whilst in point of fact it is 

 really continuous along the interdental grooves. Thus it comes 

 to pass, that in transverse sections, according to whether a 

 groove or a tooth is struck, the continuity is sometimes pre- 

 served and sometimes lost. 



The special interest attached to this structure, in a his- 

 tological point of view, is the peculiar connection of the 

 epithelium with osteogenous substance, which can otherwise 

 be scarcely regarded as an immediate substratum for a true 

 epithelium. The characters of the crista vary to a remark- 

 able extent in the different species of animals. Man, as 

 Lowenberg (39) correctly states, has the flattest, but at the 

 same time the longest crista, and the auditory teeth project 

 but slightly. The Bat appears to possess the relatively 



p, lamina reticularis ; q, a few mutilated external hair cells ; r, ex- 

 ternal epithelium of the ductus cochlearis (Claudius's cells of authors), 

 removed at s, in order to bring into view the bases of the external hair 

 cells. 



