THE EAR. 773 



series of elongated projections, 0-08 of a line long, 0-002 of a line broad, 

 which, separated from each other by shallow grooves, are slightly raised 

 at the outer end, and then suddenly depressed. Externally 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 afford a better exposition than any description. Each of them 

 represents a little rod, somewhat compressed from above to below, and 

 lies free and movable on the membranous spiral lamina, to which it is 

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

 fore, these teeth must be regarded. Viewed more closely, each of them 

 presents three joints. The innermost (n-p), an attached joint, resem- 

 bles a cell of cylinder epithelium, and contains in its somewhat dilated 

 internal extremity (o) a round nucleus, 0-005 of a line in size ; to this 

 succeed the middle joints (p, q, r) two equal, elongated, quadrangular 

 segments, 0-0044 of a line long, of the same homogeneous and glisten- 

 ing substance as that of which all these " teeth" in general are com- 

 posed (the coni articulares 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 nucleated segments attached to its 

 inner extremity, resembling pedunculated cells (s, s, s), one above the 

 other, the undermost being the longest, which may be termed " teeth 

 of the third series" (" cylinder epithelium-cells," Corti). The habenula 

 denticulata, as far as to the "teeth of the second series," is covered 

 by round or oval epithelium cells (h) which also occupy the spiral sulcus 

 below the " teeth of the first series," though lying free and separate in 

 immediate contiguity, and forming a continuous layer only on the ha- 

 mulus membranaceus. Upon these cells and over the entire habenula 

 denticulata, we then find a peculiar, thin, finely striated membrane (l-v), 

 which externally projects a little over the commencement of the zona 

 pectinata, though separated from it by some large epithelial cells (u), 

 and passing internally upon the habenula sulcata, where it is gradually 

 thinned and ultimately lost. This membrane, covered by the epithelium 

 of the cochlear canal, can hardly be viewed as anything but a continua- 

 tion of the habenula sulcata, and may be most suitably compared with 

 the zona pectinata. 



2. The zona pectinata (Todd and Bowman) (w' -w), is the outer por- 

 tion of the membranous spiral lamina, smooth on both the upper and 



