168 THE AUDITORY NERVE AND COCHLEA, BY W. WALDEYER. 



of the organ of Corti is formed upon a simple plan. Several 

 rows of columnar (twin) cells are regularly arranged, one behind 

 the other, upon a broad zone of the lamina spiralis, and are 

 firmly maintained in position between two membranous (cuti- 

 cular) boundaries (the lamina reticularis and the lamina striata 

 of the membrana basilaris.) A pair of these columnar twin- 

 cells, the pillar cells, are in great part also cuticularly meta- 

 morphosed, establishing a firm supporting arch for the whole. 

 The cuticular investing lamella proceeds from the capitular 

 pieces of the arch, and is developed from the ends of the 

 cells. It is gradually lost towards both sides in layers that 

 become progressively thinner upon the internal and external 

 epithelium. Divergences from this plan are caused by the 

 inner hair cells, which occasionally do not occur as double cells, 

 and moreover, like the internal pillars, do not correspond in 

 number to the outer hair cells. The internal pillars appear to 

 form the middle point of the whole system, whilst, both inter- 

 nally and externally, they take part in the formation of the 

 lamina reticularis. 



The careful mode of attachment of the external hair cells 

 is deserving of special notice. They are immoveably fixed, 

 and appear as though they were immoveably extended, by 

 means of their two processes and their capitular pieces, between 

 the lamina reticularis and the basilar membrane. These cells, 

 together with the pillars of Corti, constitute the distinguishing 

 peculiarity of the cochlea of Man and Mammals. I shall again 

 have occasion to refer to the hair cells, in speaking of the mode 

 of termination of the nerves. 



The apparatus to which the terminal fibres of the nervus 

 acusticus are distributed is thus constructed, and in the essen- 

 tial parts of this, the two kinds of hair cells, they actually end. 

 I shall preface their description by a few words in regard to 

 the general relations of the trunk of the auditory nerve. 



THE AUDITORY NERVE, AND ITS RELATIONS TO THE 

 ORGAN OF CORTI. 



According to the statements of Stieda (51 53), which 1 

 shall here for the most part follow, the auditory nerve arises 



