C64 THE NOSE. 



onwards with a plexiform arrangement, at first in more or less distinct 

 but anastomosing cords (fig. 477, b, 3), contained in distinct canals in 

 the bony lamina, bat after'^ards spreading out into an almost continuous 

 stratum of intermingling fibres, to be again gathered up, near the 

 edge of the osseous lamina, into conical bundles which turn abruptly 

 upwards, and passing through the elongated apertures previously de- 

 scribed, in the membranous stratum covering the bone, enter amongst 

 the epithelial structures which form the organ of Corti, in the region of 

 the inner hair-cells. 



Little is known positively with regard to the actual mode of ending 

 of the nerves amongst these structures. As they pass through the 

 apertures in the membrane, they lose their medullary sheath and dark 

 borders, and are continued as simple axis-cylinders. Their further 

 course is still a matter of doubt. Some of them are stated by Wal- 

 deyer to pass directly into the lower ends of the inner hair-cells, and 

 others to pass outwards between the rods of Corti, stretching across the 

 tunnel which these enclose, eventually ending in the outer hair-cells, but 

 these statements, although not improbable, yet require confirmation. 

 It is possible that the real termination of the nerves is to be found not 

 in the hair-cells themselves but in the subjacent irregular protoplasmic 

 cells, which both in the character of their nucleus, and in other par- 

 ticulars are not very unlike nerve-cells. 



The following numbers show the average dimensions of various parts of the 

 human cochlea. They are copied from Waldeyer (article " Cochlea " in Strieker's 

 Handbook), and represent the size in micromillimeters.* 



Cochlear canal, breadth, 1st turn ...... 800 



2nd turn 700 



„ ,, , extreme height ...... .500 



Reissner's membrane, breadth, 1st turn . . . . . 900 



„ „ 2nd turn . . . .700 



Limbus laminte spiralis, breadth, 1st turn 300 



2nd turn . . . 200—250 



Rods of Corti, space between attachment of feet . 66 — 70 



,, ., height of arch . . . . . . . 12 



., „ length of inner rods ..... .50 



„ „ length of outer rods . . . . .60—66 



Hair-cells, length of inner . . . . . . .18 



,, length of outer, with basilar process . . . 48 



,, ,, length of hairlets ...... 4 



Membrana tectoria, extreme breadth .... 200 — 2:10 



„ ,, extreme thickness ..... 50 



THE NOSE. 



The nose is the special organ of the sense of smell. It has also 

 other functions to fulfil ; — for, communicating fi'eely with the cavities 

 of the mouth and lungs, it is concerned in respiration, voice, and taste ; 

 and by means of muscles on its exterior, which are closely connected 

 with the muscles of the face, it assists more or less in expression. 



This organ consists of, first, the anterior prominent part, composed 

 of bone and cartilages, with muscles already described, which slightly 

 move the cartilages, and two orifices, anfcrior nares, opening down- 



_A micromillimeter is the irj-,r)th pai't of a millimeter, or the 25-iuot^ P^^'* ^^ ^'^ inch, 

 and is generally represented by the Greek letter fx. 



