56 AYERS. [Vol. VI. 



delicate undulations which it has been supposed to transmit, 

 and from its composition a great deal of the motion imparted 

 to it would necessarily be lost in transmission. Likewise before 

 reaching the plate of transverse fibres which form the completest 

 part of the basilar membrane as previously conceived, the motion 

 would have to be transmitted through a continuous homogene- 

 ous layer of substance lying below and inclosing the fibres 

 from the scala tympani. 



When we reduce the cochlear spiral to a straight line, we have 

 the cochlea in the form of a straight canal, receiving its nerves 

 along one side — the lower inner angle, if one may speak of 

 angles of a tube more or less oval in cross-section. The nerve 

 does not enter the walls of the tube as a continuous band, but 

 is previously divided into sub-equal sections, which form branches 

 about twice as broad as thick. There are about fifty of these 

 branches in the middle spiral of the ear of Sus and a total of 

 from no to 125 in the entire cochlea. 



Each branch of the cochlear nerve is supplied to a single 

 sense organ composed of about ten hair cells counted lineally 

 in either the row of inner hair cells or the inner row of outer 

 hair cells. There is a tendency to fuse into a continuous band, 

 owing to the suppression of the supporting cells between the 

 sense organs, which renders the determination of the bound- 

 aries of most of the organs a matter of difficulty and in many 

 cases an impossibility. Assuming that there are four rows of 

 hair cells regularly completed, each fasiculus would supply on 

 the average about forty hair-bearing elements of Corti's organ 

 in the adult. The extremes I have found are four lineal and 

 sixteen lineal with ten cells as the average length of the sense 

 organ. 



After passing through the floor of the canal the nerve fibres 

 enter the epithelial ridge and traverse the intercellular spaces, 

 branching, as they do so, until they arrive at the end cell, into 

 which they enter. The general features of the relation of the 

 nerve bundles, as they pass out of the lamina spiralis ossea 

 through the habenula perforata, during the passage of which 

 they lose their medullated sheaths, have often and accurately 

 been described, and there is substantial agreement among the 

 authorities in the matter, but the course of the non-medullated 

 fibres from the habenula perforata to their ends, and the relation 



