110 



THE EAR. 



fibrous layer and there break up into a coarse capillary network, the branches of 

 which do not, in man, pass into the tunica propria. 



The tunica propria is a clear membranous structure continuous around the whole 

 tube, although thinning off very much opposite the part where the membranous 

 canal is in contact with the bone (fig. 122, 5). Externally it is not very distinctly 

 marked off from the fibrous coat : internally it has a number of papilliform emi- 

 nences (fig. 122, 6,) which project into the interior of the canal except at the thin- 

 nest part (Rudinger). 



The epithelial lining takes the form of a complete layer of flattened cells, which 

 in the human semicircular canals are of the same nature throughout, except along 



Fig. 122. SECTION OF MEMBRANOUS SEMICIRCULAR CANAL, MUCH MAGNIFIED. (Rudinger.) 



1, outer fibrous layer ; 2, tunica propria ; 3, 6, papilliform projections with epithelial covering ; 

 f>, fixed side of the canal, with very thin tunica propria without papillae ; 7, fibrous bands passing to 

 periosteum. 



the outer part of the lumen, where there is a longitudinal tract of cells which are 

 more elongated than the rest. This line is sometimes termed the raphe of the 

 canal. 



In many of the lower animals birds and fishes some of these lining- cells are columnar, 

 while in one species of fish (Salmo hucho), as described by Rudinger, a tract along- the 

 whole length of each canal becomes developed into two rows of rounded cells, from each 

 of which a long filament extends to the wall of the canal in a direction transverse to the 

 axis. 



The ampullae, as well as the saccule and utricle, agree generally in structure 

 with the semicircular canals : but at the part where they are connected with the 

 osseous wall the fibrous outer layer is looser, and the tunica propria is much 

 thickened, and in the ampullae projects into the cavity as the septum transversum 

 surmounted by the crista acustica, before mentioned (fig. 119). Through the 

 substance of this thickening the nerve-fibres pass to the edge of the ridge, and over 

 it the epithelium is of an elongated columnar form (figs. 123 to 126), and is sur- 

 mounted by long, conical, gradually tapering filaments (auditory hairs (h), ), which 

 project stiffly into the cavity, and are about 0'03 mm. in length. These hairs are 

 borne by the columnar epithelium-cells (fig. 126), a single hair projecting from each 

 cell, but under the influence of reagents they are apt to become broken near the 

 base, and thus split up into fine fibrils which appear as a bunch of cilium-like 

 filaments attached to the free border of the cell. The columnar cells, or hair-cells, 

 do not extend down to the basement membrane, but terminate short of this in a 



