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



the labium tympanicum (of Henle) (fig. 325, a), which lies in 

 the same plane with the membrana basilaris, and with the 

 labium vestibulare forms the boundary, the swlcus spiralis in- 

 ter nus (S sp i). From the point of entrance of the nerve (fig. 

 323, a) to about the middle of its length, the organ of Corti is 

 superimposed upon the basilar membrane ; but from thence, as 

 over the rest of the internal wall, there is only a simple short 

 columnar or cubical epithelium. 



If we examine the tympanal wall after removal of the 

 membrane of Reissner, its several portions appear like so many 

 spiral girdles or zones, as shown in fig. 323. To this structure 

 the names applied by Todd and Bowman, Corti and Kolliker, 

 refer: such as the zona denticulata and pectinata, together 

 with the habenula denticulata, sulcata, perforata and arcuata, 

 forming subdivisions of the zona denticulata, and respecting 

 which the explanation of the lettering in figs. 321, 322, 323, 

 and 324, may be consulted. These terms may now be regarded 

 as obsolete. The size of the ductus cochlearis decreases, though 

 not to a very great extent, according to my measurement (see 

 the tables subjoined), as its three successive turns pass towards 

 the cupola. 



The membrane of Reissner is composed of a thin basal lamella 

 of connective tissue, supporting vessels, and covered on the 

 vestibular surface by a large-celled serous endothelium, and 

 upon the tympanal surface by a single layer of cubic cells 

 (figs. 321 and 324). 



The relations of the external wall of the membranous duct 

 of the cochlea are of a more complicated nature (figs. 321 

 and 322, e e). The already frequently mentioned cushion of 

 connective tissue, which is semilunar in section, exhibits, espe- 

 cially in young individuals, three distinct layers: internally 

 the membrana propria of the ductus cochlearis, with the stria 

 vascularis ; externally, the periosteum ; and between the two 

 a loose connective tissue, which, in embryoes, tears easily, and 

 thus permits the ductus cochlearis to be detached from the 

 cochlear capsule. The stria vascularis is a particularly vascular 

 portion of the membrana propria. Between the numerous 

 capillaries is a little adventitious connective tissue, whilst the 

 epithelium, composed of small cubic cells, rests immediately 



