ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



It is not my purpose to describe the fetal development of 

 the membrana tectoria, but it is worth while to consider briefly 

 the zones which compose the membrane; in other words, the parts 

 of the tympanic wall from which it originated. There are chiefly 



TABLE 7 



Ratios of the radial breadth of the membrana tectoria according to the turns of the 



cochlea 



Chart 4 The total radial breadth of membrana tectoria arranged according 

 to the turns of the cochlea, table 5. 



About middle part of the basal turn (I). 



About the beginning of the middle turn (II). 



About the middle part of the middle turn (III). 



About the beginning of the apical turn (IV). 2 



Chart 5 The radial breadth of the inner zone of the membrana tectoria, 



according to the turns of the cochlea, table 5. 



Chart 6 The radial breadth of the outer zone of the membrana tectoria, 



according to the turns of the cochlea, table 5. 



* In most cases when the values which have been determined are analyzed 

 according to the turns of the cochlea, it is found that they increase with later 

 growth from the basal (I) to the apical (IV) turn and in the order just given in 

 chart 4. Owing to this uniformity of behavior, some thirteen charts showing 

 the several values according to turn have been omitted, since the graph given 

 by the average value is sufficiently informing in each instance. 



In the case of those charts which have been retained, and in which the 

 measurements are according to the turns of the cochlea, the respective turns 

 I-IV are recorded by characteristic lines similar to those used for them in 

 chart 4, and in these cases the further designations of the turns are omitted. 



