DEVELOPMENT OF PERIOTIC TISSUE SPACES 



305 



which is the first indication of the formation of the marginal 

 membrane. The residual undifferentiated reticulum that does 

 not enter into the dii-ect formation of the larger spaces constitutes 

 the tissue from which is derived the adventitial coat of the 

 completed scala. 



SCALA VESTIB. 



O C S3 



--^o^ 



SCALA TYMP. 



Cr, 



cc 



D C 



n 





Fig. 2 Detail of the section shown in figure 1, enlarged 278 diameters. This 

 figure shows the part of the cochlear duct that is to form the organ of Corti, 

 and the adjacent tissue that becomes incorporated in the basilar membrane. 

 Below this is the periotic reticulum whose spaces are in the process of enlarging. 

 By repeated coalescence these spaces finally unite with the large space that 

 constitutes the scala tympani. This figure shows the histological appearance of 

 the reticulum where the formation of tissue spaces is in active operation. 



The appearance of the marginal membrane as seen in a more 

 mature space is shown in figure 3, being a detail of the margin 

 of the same scala vestibuli that is shown in figure 1. Here we 

 have a firm membrane that forms a complete barrier between 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 21, NO. 2 



