216 STRUCTURE OF THE COCHLEA. [BOOK in. 



to give rise to auditory impulses in the auditory nerve. The cells 

 of Hensen and Claudius on the outside of the outer hair-cells, and 

 the cells in the spiral groove on the inside of the inner hair-cells, 

 have doubtless parts to play; but their function is probably in 

 some way or other nutritive only, they are not immediately con- 

 cerned in the production of auditory impulses. 



833. The inner rod of Corti (Fig. 180 B) consists of a head, 

 more or less round but with flattened sides, and of a thinner 

 cylindrical body, or limb, which sloping with a gentle curve down- 

 wards and inwards ends in an enlarged foot cemented to rather 

 than fused with the basilar membrane just at its beginning out- 

 side the tympanic lip of the spiral lamina. From the head a thin 

 flat plate is continued outwards over the outer rods (Fig. 180 

 B ph., D i.r.h.). 



The outer rod of Corti (Fig. 180 B') also consists of a head, the 

 rounded surface of which directed inwards fits into a hollow supplied 

 by the head of the inner rod, while the upper surface is prolonged 

 outwards in the direction of the outer hair-cells as a long plate, 

 the " phalangar process " (B' ph.). To the head succeeds a slender 

 cylindrical gently curved body or limb, which sloping downwards 

 and outwards ends in an expanded foot cemented to the basilar 

 membrane at some distance to the outer side of the attachment of 

 the foot of the inner rod. 



The substance of which the rods are composed is peculiar. In 

 a perfectly fresh state the rods seem homogeneous or, especially 

 in the region of the limb, obscurely striated ; they are somewhat 

 easily decomposed and are readily acted upon by reagents ; under 

 the influence of hardening reagents they become rigid, and the 

 the limb is then distinctly striated longitudinally. At each angle, 

 formed by the limb and foot of the inner rod and of the outer 

 rod with the basilar membrane, is seen a nucleus surrounded 

 by ordinary protoplasmic cell substance, and a thin layer of the 

 same cell substance is continued as a delicate lining up the limbs. 

 The rods may be considered as portions of the substance of two 

 cells, represented by the two nuclei just spoken of, which have 

 become specially differentiated in nature, and in being differentiated 

 have assumed a special form. They have been spoken of as 

 'cuticular' formations, and indeed the phalangar process of the 

 outer rod is the beginning of a structure which may be considered 

 cuticular and which, consisting of rings joined together by flat 

 bars, or " phalangae," stretches outwards so as to form a covering 

 over the whole region of the outer hair-cells (Fig. 180 D). Through 

 the holes of the rings of this reticulate membrane, membrana reticu- 

 t lata as it is called, the heads of the outer hair-cells project, and 

 processes from cells which we shall presently describe as connected 

 with or forming part of the outer hair-cells are attached to the 

 bars between the rings. The word " phalangae " means the poles 

 on which a burden is slung between two men's shoulders ; and the 



