312 O. VAN DER STRICHT 



11. The second, third, and fourth spaces of Nuel are located, 

 respectively, between the first and second, the second and 

 third, and the third row of hair cells and the cells of Hensen 

 (atrophied hair cells of a fourth row). These spaces do not 

 extend do^^^l between the sustentacular elements, but communi- 

 cate with each other and with the first space through clefts 

 between the hair cells. These intercellular channels, originally 

 occupied by the phalanx processes of the sustentacular elements, 

 become free after the shifting of the latter into the neighboring 

 medial spaces, the phalanx processes of the cells of Deiters of 

 the third row remaining in situ. 



12. Each of these phalanx processes is composed of an axial, 

 fibrillar filament and a peripheral, clear, cytoplasmic sheath. In 

 the course of development this sheath becomes thinner and may 

 disappear by a process of secretion, which gives rise to the fluid 

 contents of the primitive second, third and fourth spaces of 

 Nuel. 



13. The roofs of the second, third, and fourth spaces of Nuel 

 and of the intercellular clefts between two neighboring hair 

 cells of each sensory row are made up of delicate membranes, 

 partially fibrillated, which betong to various parts of the pha- 

 langes of the sustentacular elements. 



14. The fluid contents of the tunnel and the first space of 

 Nuel are separated from the fibrillated basement membrane of 

 the membrana basilaris by a thin protoplasmic covering, be- 

 onging to the feet of the inner and outer pillar cells. They 

 ntercommunicate through clefts between the outer pillars and 

 communicate with those of the second, third, and fourth spaces 

 of Nuel. The fluid of all the spaces of Nuel is separated from 

 the endolymph of the cochlea duct by the roofs of these inter- 



.stices, very thin membranes, entirely or partially fibrillated. 

 Such structures doubtless promote the propagation of vibratory 

 waves from the basilar membrane to the membrana tectoria, 

 contained in the cochlear canal. 



All the material and reagents necessary for the present investi- 

 gations were suppUed by Dr. T. Wingate Todd, Director of the 



