202 AVERS. [Vol. VI. 



add anything to the facts already discovered by the German 

 anatomists. In the following paragraphs I give the main feat- 

 ures of the cochlear ontogeny of the Rabbit as given by Ret- 

 zius, with whom I agree, except in the cases noted further on. 



Development of Rabbif s Ductus Cochlcaris. 



■I. In the Embryo. 



The papilla acustica basilaris develops in the first ten days 

 after birth — i.e. it acquires its maturity, and for the main part 

 ends its development during this time. From the beginning on 

 the canal is strongly depressed on its vestibular side. The duc- 

 tus cochlearis consequently forms throughout most of the embry- 

 onic life a flattened epithelial tube whose walls are composed of 

 cylindrical cells, the whole tube being inclosed in connective 

 tissue (the so-called mucous tissue or Schleimgewebe of the 

 Germans). At first there is no distinction to be noted in the 

 structure of its walls. The floor, or neural wall, however, thick- 

 ens early, and soon thereafter develops the so-called epithelial 

 ridges. The manner of growth of the organ has not been 

 satisfactorily made out, but the organ of Corti, as well as the 

 tube, grows progressively away from the basal portion. Inter- 

 stitial growth is certainly not proven to occur. 



Retzius found the first trace of Corti's pillars and their inner 

 neighbor cells to reach upward from the basilar membrane as 

 two triangular cells whose bases are below, while their narrowly 

 truncate upper ends lie in border angle between the large and 

 small folds or epithelial ridges. 



Just within from these occur the inner hair cells already laid 

 down and provided with hairs. These cells, then, belong to the 

 larger fold, and are placed in its outer border. The direction of 

 these cells is, as in the adult animal, oblique from below and 

 within upward and outward. The three rows of outer cells lie 

 without the pillars and belong to the smaller epithelial fold. 

 They are already in the embryo, i.e. before birth, laid down as 

 hair-bearing cells in all of the spires. They are bottle-shaped, 

 granular cells, carrying their nuclei in the lower parts of their 

 cells. Their hairs are short and more or less perpendicular. The 

 hairs of the third row are slightly inclined inward and upward. 



The supporting, or Deiters's, cells project upwards among the 

 hair cells from their broad basilar ends, and end pointedly be- 



