772 SPECIAL HISTOLOGY. 



zone, whilst in the last half turn it is bounded only by the expansion of the 

 nerve, so that the habenula sulcata, in the strict sense of the word, properly 

 constitutes, in this situation, only a part of the so-termed membranous 

 spiral lamina. On the upper surface of this layer, and on the outer border 

 of it, there is an uninterrupted series of clear, peculiarly glistening, 

 elongated, slightly clavate processes (g), the " teeth" as they are termed 

 "of the first series," which, in the first spiral turn of the cochlea, are 

 0-02 of a line long, O'004-O-OOo of a line wide, and 0-003 of a line 

 thick, at their origin, whilst in the last turn they are not more than 

 0-015 of a line long and 0-003 of a line broad. They project, free, 

 into the scala vestibuli, and arch over the commencement of the habenula 

 externa, so that between the two a tolerably deep sulcus, semicanalis 

 spiralis (Huschke), opening externally, is left. Towards the axis of 

 the cochlea the so termed "teeth" are directly continuous, with simi- 

 larly constituted, elongated ridges or costce (Fig. 309 a a), which are 

 occasionally conjoined in pairs, or divided into two, and still further 

 inwards break up into divisions, which become shorter and shorter and 

 smaller and smaller, being at first elongated and afterwards rounded. 

 In the longitudinal and transverse grooves between these costce and 

 tubercles and the teeth, there usually exists, in single series, rounded 

 or elongated, opaque glistening corpuscles (e), 0-0015-0-002-0-003 of 

 a line in size, which, on the addition of acetic acid, prove to be nuclei ; 

 and by the same reagent, nucleiform strice occasionally become distinct 

 in the pale and somewhat swollen "teeth" and costce, which parts, 

 consequently, as well as those presently to be described, I am inclined 

 to regard as belonging to the connective-tissue group. 



The habenula externa s. denticulata (h-t) arises under the base of the 

 "teeth" of the first series, directly from the just-described habenula 

 sulcata, and constitutes at first the bottom of the spiral sulcus noticed 

 above. In most places its thickness does not amount to more than 

 O'OOl of a line, which is also that of the rest of the membranous spiral 

 lamina, that is to say, of the zona pectinate, and its width increases 

 towards the cupola in proportion to the decreasing breadth of the habe- 

 nula sulcata, so that it measures at first, not more than 0*05, and ulti- 

 mately, 0-1 of a line. 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 ele- 

 vations, proceeding from within to without, are as follow : first, come 

 the so-termed " apparent teeth" (" dents apparents," Corti), a crowded 



sulcata : $, spot where a " tooth of the first series " originates ; y, spaces between the " ap- 

 parent teeth ;'' J 1 , anterior portion of a " tooth of the second series " thrown back ; s, the same 

 in its natural position, without its epithelial cells; , the same with only the lowermost 

 epithelial cells ; , the same with two of the lowermost cells ; &, streaks or slight elevations 

 of the zona pectinata : x, periosteum, by which the lamina spiralis is attached, with spaces, 

 A, between the bundles. After Corti. 



