DEVELOPMENT OF THE ORGAN OF CORTI. 



outer hair-cells. Subsequently the rods of Corti become formed by a transformation 

 of the protoplasm of other of these columnar cells, and the cells of Deiters also 

 begin to appear. In the meantime the epithelium of the vascular stria which was 

 at first similar to that of the rest of the canal becomes pigmented and vascularized, 

 and the remaining epithelium of the cochlear canal is also gradually acquiring the 

 form and character by which its various parts are distinguished. 



The membrana tectoria appears to be formed as a cuticular deposit or secretion 

 from the epithelial cells of the limbus, upon which, even at a comparatively early 

 stage of development, it may be seen to lie. 



Measurements of some of the parts of the cochlea. The following 

 numbers (from Eetzius) show the average dimensions of various parts of the 

 human cochlea, and represent the size in micromillimeters. 



Cochlear canal, breadth, basal turn 0'45 



middle ... 0*77 



apical . . . . 0-80 



extreme length 35-00 



Reissner's membrane, breadth, basal turn . . . . 0*81 



middle 0'88 



apical . . 0-85 



Limbus laminse spiralis, breadth, basal turn .... 0*24 



middle . . 0'23 



apical . 0-22 



Rods of Corti, space between attachment of feet, basal turn . 0*048 



middle . 0-081 

 apical . 0-09 



height of arch, basal turn . . ... 0*028 



middle .... 0-045 



apical . . . . 0-049 



length of inner rods . . .0-0480'07 



length of outer rods . . . . 0*06 0*1 



Hair-cells, length of inner 0*0180-024 



length of outer 0*030-04 



,, length of hairlets .... . 0-005 



Membrana tectoria, breadth ... . 0'28 0'34 



extreme thickness . . 0'025 



Basilar membrane, breadth from habenula perforata to lig. 



spirale, basal turn 0'21 

 middle 0-34 

 ,. apical ,, 0-36 

 breadth from habenula perforata to feet 



of outer rods, basal turn 0*075 

 -. middle,, 0-12 

 apical 0-126 



RECENT LITERATURE OP THE EAR. 



Altzheimer, A., Ueber die Okrenschmakdrusen, WUrzburg, 1888, 



Ayers Howard, Die Membrana tectoria ioas sie ist, und die Membrana basilanswas sic 

 verrichtet, Anatomischer Anzeiger, vi. 1891 ; Ueber das peripherische, Verhalten dcr Miornerven, 

 Anat. Anz., 1893. ... . 



Bag-insky, G-., Zur EntwicU. der Gehorsehuecke, Arch. f. mikr. Anat., xxvin. 11 



Barth, A., Beitraffe zur Anatomic des Ohres, Zeitschrift fur Ohrenheilkunde Band xvn. ; Ueber 

 die Darstdlung des h&utvjen Labyrinthes, Archiv fur Anatomie und Physiologie, Physiol. Abt., Jahrg. 

 1889 ; Beitrag zur Anatomie der Schnecke, Anatomischer Anzeiger, iv. 1889. 



