410 SPECIAL HISTOLOGY. 



the rest of the membranous spiral lamina, that is to say, 

 of the zona pectinata, and its width increases towards the 

 cupola in proportion to the decreasing breadth of the 

 habenula sulcata, so that it measures at first, not more than 

 0-05'", and ultimately, 1'". With respect to its structure, it 

 presents, on the side of the scala vestibuli, a considerable 

 number of elevations, whilst towards the scala tympani it is 

 perfectly smooth and even. These elevations, proceeding from 

 within to without, are as follow: — first, come the so-termed 

 "apparent teeth" ("dents apparents," Corti), a crowded series 

 of elongated projections, O'OS'" long, , 002 /// broad, which, 

 separated from each other by shallow grooves, are slightly 

 raised at the outer end, and then suddenly depressed. Exter- 

 nally to these processes which, in the first turn of the cochlea, 

 are still situated on the zona ossea, beneath the " teeth of the 

 first series," and in that situation present minute elongated 

 hollows between their outer ends (fig. 309, y), but in the 

 second and third turns are placed more externally than the 

 " teeth of the first series," being bounded on the under surface 

 only by the nerves, succeed in equal number the " teeth of the 

 second series," (Corti) (n-t), very remarkable structures, of 

 which the adjoining figure will affbrtl a better exposition than 

 any description. Each of them represents a little rod, some- 

 what compressed from above to below, and lies free and 

 moveable on the membranous spiral lamina, to which it is 

 affixed only by the inner extremity, as a continuation of which, 

 therefore, these teeth must be regarded. Viewed more closely, 

 each of them presents three joints. The innermost (n-p), 

 an attached joint, resembles a cell of cylinder epithelium, and 

 contains in its somewhat dilated internal extremity (o) a round 

 nucleus, O'OOS"' in size; to this succeed the middle joints 

 (p, q, r), two equal, elongated, quadrangular segments, 0-0044'" 

 long, of the same homogeneous and glistening substance as 

 that of which all these " teeth * in general are composed (the 

 coni articular es of Corti), which are connected with each other 

 and with the internal and external joints, so as to allow the 

 latter a certain extent of motion up and down. The last joint, 

 finally (r-t,) is at first attenuated, but towards the extremity 

 again becomes wider and bifurcate, and supports three nucle- 

 ated segments attached to its inner extremity, resembling pe- 



