SECT. 234.] STRUCTURE OF BASILAR MEMBRANE. 



59* 



Fig. 243. 





ning to the end of the cochlear canal. In the first and second 

 turns of the cochlea, its under surface lies in 

 the place of the periosteum, on the outer edge 

 of the osseous spire; but in the last half-turn, 

 it is only limited by the nervous expansion, so 

 that the habenula sulcata is here, in strictness, 

 a part of the membranous spire. I find the 

 habenula sulcata to consist of a dense connective 

 tissue, almost homogeneous, but having a few 

 stellate plasmatic cells and scattered capillaries. 

 On its upper surface, at the outer margin, there 

 is found an uninterrupted series of elongated 

 projections, transparent and with a peculiar 

 lustre, somewhat expanded at their extremities ; 

 these are the so-called 'teeth of the first series,' 

 which, according to Corti, measure cr02'" long, 

 0"004'" to 0-005'" broad, and o , oo3'" thick, at 

 their commencement in the first turn of the 

 cochlea, while in the last turn they exhibit a 

 length of only 0-015'", and a breadth of 0'003'". 

 These teeth project, with their one side free, 

 into the scala vestibuli, and with their points, 

 to which the membrana Cortii is attached, arch 

 over the commencement of the habenula ex- 

 terna, so that between the two there results a 

 pretty deep furrow, opening externally into the 

 scala media, the semicanalis spiralis of Huschhe ; 

 in the ox, this remains open for 004'" in depth 

 (fig. 241). Towards the axis of the cochlea, /< 

 the above-mentioned teeth are directly con- 

 tinued into similar elongated prominences or 

 ribs (fig. 24.?), which occasionally co- _ . . ., , . ... 



\ & to/ > J Surface of the lamina spiralis mem- 



alesce or separate in pairs, and still br ™ a f "> e surface which is tnrnedto- 



^ ~ ^ v,j_. L wards the scala vestibuli; magnified 



further inwards break up into shorter 225 diameters. The lettering is partly 



the same as that of fig. 242. aa. cylin- 



and smaller pieces, at first elongated, dr j cal prominences of the habenula sut- 



■i ° cata; /3. place where a tooth of the first 



and afterwards round. In the longi- seriesteok origin ; y.for^taa between 



° the aentt apparent* ; S. the anterior 



tudinal and transverse ffrOOVCS, which portion of a tooth of the second series, 



# turned down ; e. a similar tooth in situ, 



are found between these ribs and pro- without its epithelial ceiis ; £ a similar 



x tooth with only its lowest epithelial 



mineuces, and the teeth, there exists a <*"; i- another with the two lowest 



cells; 0. striae or Blight prominences 



simple series of dark shining corpuscles m tiie '■■■ " pecHnataj *. periosteum 



1 i giving attachment to thclaminaspiralis, 



(figS. 2A2, 2±7, e), rOUlldish Or elongated, witl > spaces, A, between the fibrous 



° bundles. After Cnrti. 



coo^'" to 0-002"' in 





- 



and measuring 



