THE VERTEBRATE EAR. 347 



EXPLANATION OF PLATE VI. 



Fig. I. A transverse section of the cochlear organ of an S^-inch Pig embryo. 

 X 285. s.ex., l.e.r., small and large epithelial ridges, c.c, cochlear canal, s.c, sup- 

 porting cells, h.b., hair band, c.n., cochlear nerve, g.c, cochlear ganglion, ni.b., 

 membrana vasilaris. c.p.c, Corti's pillar cell, which has not divided into the inner 

 and outer cells, s.t., scala tympani. 



Fig. 2. Transverse section (radial) of the cochlea of the house Mouse (adult). 

 X 114. To show the length and relation of the hairs of the hair band, o.c, organ 

 of Corti. S.V., scala vestibuli. s.t., scala tympani. s.v., stria vascularis. m.R., mem- 

 brana Reissneri. 



Fig. 3. The apical spire of the cochlea of a 19 cm. Pig embryo, o.c, organ of 

 Corti. c.c, Corti's canal; the arrow lies over the lamina spiralis ossea, magnified 

 about 20 diameters. /., the apex of the epithelial ridge. No helicotrema is developed. 



Fig. 4. The distal end of the cochlear tube of the Mocking-bird, with the lagenar 

 bulb. I.e., c, and f.', the cartilaginous framework on which is stretched the mem- 

 brana basilaris {in.b.'). o.m., the otolithic mass lying over the lagenar sense organ. 



X90- 



Fig. 5. Surface view of three cochlear sense organs from the adult human ear. 

 i.e., inner hair cells. oc?—oc'^, rows of outer hair cells. The rows of sense cells are 

 seen to be more and more incomplete the further they are removed from the inner 

 edge of the organ. Only the outlines of the hair-cell caps are drawn in. After 

 Retzius. 



Fig. 6. The lageno-cochlear tube of the Mocking-bird seen from its neural face. 

 n.p.b., n. papilla basilaris. b.v., blood-vessel, r.l., ramulus lagenas n.p.b. cochlear 

 nerve, a.m., the otolithic mass lying over the lagenar sense organ, e.e., cochlear 

 canal, b., the isolated otolithic mass, to show its zones and peculiar shield shape. 

 c, to illustrate the tortuous course of the main vascular trunks in the roof of the 

 cochlear canal or the stria vascularis. X 10. 



Fig. 7. Surface view of the sensory hair cells of the basilar organ of the Mocking- 

 bird's ear. X 1400. h.c, hair cell, h., one of the several hairs springing inde- 

 pendently from the top of the cell, s.e., supporting cell. 



Fig. 8. Surface view of ampullar sense organ of the Mocking-bird. X 45- 

 Showing the several crests composing the crista acustica. p.e., projecting axial 

 crests, a.c, apical crest, p.s., planium semilunatum. cw., canal wall. 



Fig. 9. A view of the auditory hairs from five hair cells of the papilla lagenge of 

 the Mocking-bird. X 850. a, the hairs, more or less torn and spread into a brush. 

 b, c, and d, normal slender hairs, e, an exceptionally strong hair. Living preparation. 



Fig. 10, An oblique view of a piece of the membrana tectoria or hair band of 

 the Mocking-bird, ep., epithelium, a, the general course of the striations and lines 

 of lacunse. /., the perforating lacunale of the band. X 510. Chrom-osmic prep- 

 aration. 



Figs. II and 12. The acustico-facial nerves and ganglia of a human embryo 

 22 mm. long. X 25. The figures are drawn from a model of these structures as 

 found on the left side. After W. His, Jr. 



