1^8 AVERS. [Vol. VI. 



Zelle (Bodenzelle) hinzustellen ; er gehort zum Stabchen, wie 

 audi Kolliker behauptet hat und wie ich noch genauer fur 

 ervvachsene Individuen nachvveisen will." 



From my own observations I am confident that division begins 

 below and works upward into the heads. In some cases, these 

 never become completely separated, and thus is given firmer 

 union to the two elements of the arch of Corti. The undivided 

 part is in all cases only the cell wall which incloses the fibres of 

 Corti's rods. 



The view which all previous authors have held with reference 

 to the nature and origin of the membrana tectoria (so-called) is 

 that this structure was a cell secretion and was poured out by 

 and upon the upper ends of the cells forming the surface of the 

 organ of Corti. Boettcher, however, more consistent than other 

 observers, maintained that this was the only product of the cell 

 activity, while others claimed that besides the membrana tectoria 

 the cells, by a process unknown, or similar, produced the short 

 rod-like structures known as auditory hairs (Gehorstabschen). 

 These hairs were supposed to be formed in such a way that 

 they projected into the membrana tectoria's substance in holes 

 either preformed or produced by the growth of the hairs into it. 



According to Boettcher's observations on the Sheep (and my 

 preparations of the Pig confirm his statements so far as the 

 time of appearance of the hair band is concerned) the first trace 

 of this structure is to be seen in the 5.5 mm. embryo. The 

 epithelial ridges are not yet distinctly formed, and the mem- 

 brana tectoria simply lies over the thickest part of the floor as 

 a thin radiately striated plate. 



After working over preserved material without satisfactory 

 results, Boettcher says {loc. cit. p. 123): "Auch an der mit 

 Vorsicht in Humor aqueus isolirten Corti'schen Haut lasst sich 

 kein befriedigendes Resultat liber die ganze Ausdehnung der- 

 selben gewinnen. Sie erscheint weich, aber in hohem Grade 

 elastisch. Der diinnere hyaline und der dickere streifige Theil 

 kdnnen durch eine langsverlaufende Linie nicht gegeneinander 

 abgegrenzt werden. An den Schnittrandern nimmt man ge- 

 wohnlich nur ein seichtes Abschwellen und dann wieder ein 

 Anschwellen der streifigen Zone wahr, bevor sie mit leicht 

 abgerundetem Rande aufhort." 



Boettcher describes this structure as he found it in the 15 cm. 



