DEVELOPMENT OF THE ORGAN OF CORTI 293 



the two fibrillated hands. This rather deep portion of the 

 pillar, situated at the level of the lower poles of the outer hair 

 cells (oh^), doubtless belongs to the developing head. From 

 this it is evident that the superficial, thin, tapering segment of 

 the outer pillar cells, which gives rise to both the phalanx process 

 and the head, attains more than one-third (figs. 1 and 3, op) or 

 about one-half of the entire length of the cell, or about the length 

 of the outer acoustic element {oh^), although no distinct demar- 

 cation can be observed between the future head and the pillar 

 body. 



Two other features lend support to this view: the existence of 

 an abundant, vacuolated cytoplasm along the intermediate 

 portion of the cell, the future pillar body, which only slightly 

 encroaches upon the lower part of the future head, and the 

 presence of terminal bars or rather true intercellular, obturating 

 partitions. These have been observed and termed 'bandelettes 

 obturantes' by N. Van der Stricht ('08) and 'Kittsubstanz' or 

 'Kittlinie' by Held ('09). This material stains intensely with 

 iron hematoxylin like the superficial terminal bars with which 

 it is in continuity, and corresponds to them in nature and 

 chemical constitution. It gives rise not to 'lines' or 'bars,' but 

 to true septa, uniting parts of the cells and obturating the 

 subjacent intercellular spaces. These partitions exist not only 

 between contiguous developing and definitive heads of inner and 

 outer pillars, but also between the apical surface (that turned 

 toward the apex of the cochlea) and basal surface (that turned 

 toward the base of the cochlea) of the heads of each spiral row. 

 On the other hand, they are altogether lacking along the medial 

 surfaces of the heads of the inner pillars and the lateral surfaces 

 of those of the outer (figs. 1 and 3, tb). 



The second stage of development is characterized by a rapid 

 enlargement of the future head of the outer pillar (fig. 4, ohd), 

 so that it reaches the site of the intermediate portion or even 

 surpasses it, when the process of cytolysis progresses along the 

 tunnel space (fig. 7, op). At first the head remains smaller next 

 to the surface, but soon this portion expands and becomes 

 somewhat larger than the deeper part (fig. 4, ohd) and acquires 



