

VIEW OF THEIR ANATOMY AND DEVELOPMENT. 137 



four months, the development of the scalse commences ; as well 

 as of the parts contained in the duct (fig. 320). 



The former originate in the retreat (Verfliissigung) of the 

 mucous tissue, to the two sides of the ductus cochlearis (see 

 fig. 320, where this tissue still remains in the last coil), whilst, 

 in order to form a septum between the two coils, it undergoes 

 ossification, the cartilaginous capsule however, participating 

 to some extent in the process (fig. 320, d). Moreover a cord 

 proceeding from the duct, and extending to the axis of 

 mucous tissue, remains persistent, in which at a very early 

 period the fibres and ganglion cells of the auditory nerve are 

 visible (L sp and Gl in fig, 320). This cord partly ossifies 

 near the axis, forming the lamina spiralis ossea, and always 

 continues to be fused in a peculiar manner with the fibrous 

 menibrana propria of the canal, which is already capable of 

 being demonstrated as a special layer. The membrana propria 

 is developed in exactly the same manner out of the mucous 

 tissue around the ingrowing epithelial tube, as is the theca 

 of the Graafian follicle, or the fibrous wall of t*he utriculus 

 and semicircular canals. We find here a recurrence of the 

 same process as that stated by His (69) to occur in the develop- 

 .ment of epithelial masses in a matrix of connective tissue. 

 The epithelial structures appear to exert a formative stimulus 

 upon the fibrous investment, resulting in an abundant cell 

 proliferation immediately around the epithelial tube, from 

 which at a subsequent period the membranse proprise of the 

 originally naked epithelial masses are developed. We learn 

 these facts, especially in reference to the ductus cochlearis, 

 from the illustrations of E. Rosenberg (49), the correctness 

 of whose fig. 1, in plate ii., I can entirely confirm. Ultimately 

 the mucous-tissue axis of the cochlea, in which the nerve 

 fibres are imbedded, also ossifies. In all the ossified parts 

 remains of the mucous tissue persist in the form of a delicate 

 periosteum. A proper perichondrium is indeed visible at an 

 early period on the inner wall of the cochlear capsule, and 

 with this the remains of the mucous tissue of the scalse subse- 

 quently coalesce. 



The epithelium of the ductus cochlearis (fig. 320, e <? 4 ) is 

 genetically identical with the epithelium of the labyrinth- 



