No. I.] THE VERTEBRATE EAR. ny 



or descend out of the layer from the cell row to which they 

 belong, and in any given transverse section the hairs from the 

 different rows appear to be of about equal length, so that the 

 hairs of the outer row of sensory cells end on the upper sur- 

 face before those of the next succeeding row by about the 

 same interval that separates the rows of cells, and so for all 

 the rows. In this manner the middle of the plate must neces- 

 sarily be the thickest, while the inner edge of the band would 

 be composed of only those hairs reaching inward from the inner 

 row of cells. 



Most previous authors have maintained, as I have shown 

 in the historical introduction to this chapter, that the mem- 

 brana tectoria was composed of isolable fibres held together by 

 a common, more or less gelatinous matrix, the " Zwischensub- 

 stanz " or ground substance. I have examined many hair bands 

 with the greatest care, using all the chemical and physical tests 

 known to me, but have failed to detect a tissue, stuff, or deposit 

 of any kind in the hair band between the hairs which was at 

 all general in its occurrence or could possibly come under the 

 head of a matrix for the fibres of the membrana tectoria as 

 described by the older authors. According to my view of the 

 nature of the hair band, and according to anatomical facts as I 

 have found them, the hair band would not have a capillary 

 matrix under normal conditions. It is true an excessive secre- 

 tion of mucus in the ear might in a supposable case so coagu- 

 late as to imbed the hairs in a common mass, but I have never 

 met with such a case, and I do not think mucus or any other 

 albuminoids are produced inside the ear canals as they exist in 

 living vertebrates, in sufficient quantities to give rise to such 

 appearances in histological preparations. 



The only conclusion admissible is that observers who have 

 recorded the presence of such a matrix have had to do with 

 pathological conditions, or post mortem changes, largely due 

 perhaps to the reagents used. 



It is a matter of importance as well as great interest to deter- 

 mine as nearly as may be the exact physical conditions of the 

 parts of the nerve-end apparatus which are concerned in trans- 

 mitting the physical energy, in the common acceptation of the 

 term, into nerve energy. 



Retzius, among others, and with more complete data than 



