Fig. 242. 



*$- 



590 LAMINA SPIRALIS OF COCHLEA. [SECT. 234. 



of the lamina spiralis has a constant breadth 

 of o't!" , and divides into the two membranes 

 already mentioned with the intermediate 

 space, the scala media, between them. Each 

 of these parts deserves a more particular 

 description. 



The lamina spiralis membranacea, in its 

 more restricted sense (excluding the mem- 

 brana Cortii), is also called the basilar mem- 

 brane, and may best be divided with Corti 

 into two portions, a zona dentieulata, and 

 a zona pectinata. The former of these occu- 

 pies about the inner two-thirds, the latter 

 about the outer third of the breadth of the 

 membranous lamina spiralis ; they are both 

 distinguished by a great complexity of struc- 

 ture, which has recently been the subject of 

 a remarkable work by Corti; and, since this 

 author, additional observations have been 

 lately made by myself, Claudius, Reissner, 

 Bdttcher, and M. Schultze. Figs. 242, 243,244, 

 and 245, will assist in the explanation of these 

 difficult structures; the two figures Avhich 

 have been taken from Corti are indeed faulty 

 in several respects, but 'they are indispensably 

 necessary to the right understanding of the 

 nomenclature adopted by this writer.  



A. The zona dentieulata of the basilar 

 membrane (tigs. 242, 243, d-v) is again to 

 be resolved into two portions, the one inter- 



Perpendicular section of the lamina spiralis, six ual, the liabenula interna S. 



lines distant from its commencement, magnified about , 



225 times. Prom the cat or dog. The epithelial layer sulcata ( d-O), the Other ex- 



which covers the upper and under surface is omitted. , v , _ z 



a. periosteum of the zona spiralis ossea; b. the two layers tei'lial, the llOLOenUlCL externa 



of the lamina spiralis ossea near the free border ; e, c', c". - -. . 



termination of the auditory nerve ; d-w. lamina spiralis S. dentieulata Ul-t). I lie 



membranacea; d-w'. zona dentieulata; d-d'-f.hauenula e . ' 



sulcata; d. spot where the periosteum becomes thick- IOl'mer IS immediately prO- 



ened ; e. nuclei in the grooves of the liabenula sulcata;  i / ; ,i • i 



f-g. teeth of the first series; g-f-h. sulcus s. semicanals lOllged (at the point marked 



spiralis; h. lower wall of the same; k. epithelial cells at Jx v ,, 



the entrance of the semi-canal; h-w' haberada denticu- Ct) irom the periosteum 01 



lata; hm. apparent teeth; n-t. teeth of the second ,1 , 



series ; n-p. posterior segment of the same ; 0. enlarge- the OSSeOUS ZOUe, Oil that 



ment with a nucleus on it; p-q. and q-r. articular pieces; r ., ■. •. . , . . 



r-t. anterior segment of the second series; s,s,s. three aspect 01 it Ollly WlllCll looks 



cylindrical cells, seated upon it ; b-v. membrane which 1j.ii 



covers the liabenula dentieulata; u. one of the epithelial tOWamS the SCala tympani ; 



cells beneath it; 10-vf. zona pectinata; x. periosteum •, i -, -. , , 



which fixes the lamina spiralis (muse, cochlearis, Todd It decreases m bread til and 



and Bowman); y. vas spirale internum; z. its inner ,i • i n .-. , 



coat. After Corn. tlnckness trom the begin- 



