DEVELOPMENT OF PEKIOTIC TISSUE SPACES 315 



lection, No. 1400-30). Attention has already been directed to 

 these figures in the description previously given of the cistern. 

 The scala vestibuli can be seen in figure 6. Above, it opens 

 freely into the cistern and extends downward along the apical 

 side of the duct as a single main space, possessing a rather uni- 

 form diameter. It extends along the first two turns of the duct, 

 gradually tapering off and showing a less mature character in 

 its distal portions. Along the second turn of the duct the spaces 

 are incompletely fused and the contour becomes correspondingly 

 irregular. As a rule the peripheral margin of the scala seems 

 less mature and more irregular than the central margin. The 

 scala- vestibuli does not connect with the scala tympani at any 

 point as yet. The two are separated in the first place by the 

 cochlear duct and then more centrally by a framework of con- 

 nective tissue in which are the radiating bundles of the cochlear 

 nerve with the nodes of ganglion cells that form the spiral gan- 

 glion. These latter structures are not shown in the model, they 

 occupy however the V-shaped groove seen between the two 

 scalae. 



The scala tympani, as can be seen in figure 7, extends downward 

 on the basal side of the cochlear duct along its first two turns. 

 This corresponds to about the same linear dimension as that of 

 the scala vestibuli. In its proximal portion it shows a greater 

 area in cross section than the latter, but further toward the 

 apical region it is about the same size and in some places it is 

 even smaller. The peripheral margin of the scala tympani is 

 distinctly more irregular than the central margin. This irreg- 

 ularity is due to spaces along the margin that are actively 

 coalescing with the main space, but in which the fusion is not 

 yet complete. The irregularity of this margin is thus an indi- 

 cation of the direction of the expansion of the scala. As the 

 diameter of the whole cochlear mass increases it is evident that 

 the main growth of the scala must radiate outward in a periph- 

 eral direction. This is accomplished by the continual assimi- 

 lation of new reticular spaces along this margin. At the proximal 

 end of the scala tympani can be seen an oval depression which 



