DEVELOPMENT OF THE ORGAN OF CORTI 311 



8. The first space of Nuel, which, in the adult organ of Corti, 

 is situated between the outer pillars and the outer hair cells and 

 the cell bodies of the sustentacular elements of the first row, 

 appears as an intercellular cleft, within which is accumulated a 

 fluid discharge from the outer pillars. At the lateral surfaces 

 of the latter project clear secretion vesicles, which undergo a 

 process of cytolysis and liquefaction. The exudation of this 

 fluid seems to be due to a difference of pressure, on the one hand 

 within the medial vacuolated cytoplasmic zone of the outer rods 

 of Corti, and on the other, at their lateral surface. It is pro- 

 moted by the shifting of the embyronic pillars from the first 

 spiral row of outer hair cells towards the inner rods of Corti, by 

 the development of laterally enlarged segTiients at the tw^o 

 extremities of the outer pillars, the foot and the head, and an 

 elongation of the outer pillar bodies, only possible by virtue of 

 an incurvation, the concavity being turned towards the cleft of 

 Nuel. 



9. This process of cytolysis is manifest at the level of the 

 heads of the outer pillars. Indeed the enlarged embryonic head 

 is more bulky than the adult head, and the phalanx process, 

 shorter in the earlier stages of development, later becomes 

 longer. Originally the phalanx process is represented by two 

 segments, a subphalangeal and an intercellular segment, the 

 latter running between two hair cells. Later on, a submem- 

 branous segment appears. This lies beneath the lateral portion 

 of the head plates of the inner pillars, and is developed from a 

 lateral part of the enlarged outer head by a process of disin- 

 tegration of clear cytoplasm, which encloses the horizontal 

 intracephalic fibrillated bundle. 



10. The roof of the first space of Nuel in the earliest stages of 

 development of this interstice is composed of two uninterrupted 

 coverings, one superficial and very thin, the lateral portions of 

 the head-plates of the inner pillars, the other deeper and much 

 thicker, the lateral parts of the outer heads. In the adult 

 cochlea this roof is made up of the same parts of the superficial 

 head-plates and a largely interrupted covering, the equidistant 

 submembranous segments of the phalanx processes. 



