THE EAR 



1557 



the inner rod receives the round portion of the head of the outer 

 rod. Finally, the inner rods are shorter than the outer rods. 

 The outer rods are less numerous and longer than the inner, 

 and they incline upwards and inwards. The head of each is 

 divisible into two parts — inner and outer. The inner part is round, 

 and is received into the concavity on the outer aspect of the head 

 of the inner rod. The (yider part is prolonged into a beak-like pro- 

 jection, called the phalangeal process, which forms part of the lamina 

 reticularis, to be presently described. 



Fig. 653. — The Organ of Corti (Wiedersheim, after Lavdowsky). 



1. Spiral Ligament 



2. Ljmbus 



3. Sulcus Spiralis 



4. Inner Rod of Corti 



5. Outer Rod of Corti 



6. Tunnel of Corti 



7. Phalangeal Process of Outer Rod 



8. Inner Hair^cells 



9. Outer Hair-cells 



10. Cells of Deiters 



11. Lamina Reticularis 



12. Cells of Hensen 



13. Cells of Claudius 



14. Spiral Ganglion 



15. Cochlear Nerve 



16. Nerve-fibres to Hair-cells 



The auditory or hair-cells are arranged in two sets — inner 

 and outer. The inner hair-cells are situated internal to the 

 row of inner rods, and are disposed in a single row. They are 

 from 3,000 to 4,000 in number. Their free extremities, which 

 lie close to the heads of the inner rods, are each provided with 

 a tuft of short, hair-Hke filaments. The deep, nucleated ends of 

 the cells are related to the terminal arborizations of nerve-fibres. 

 Internal to the row of inner hair-cells there are two or more rows 

 of columnar cells, which are continuous with the columnar epi- 

 thelium of the sulcus spiralis laminae. The outer hair-cells are 

 •disposed in three or four rows external to the outer row of rods. 

 They are much more nmnerous than the inner hair-cells. Their 



