PROPORTIONS OF THE TECTORIAL MEMBRANE 



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a little longer than that of the fetus at term, but hardly more 

 than 1 mm. longer. 



The width of the tectorial membrane varies considerably. 

 It is widest in the apical turn of its coil and tapers thence gradual- 

 ly and regularly to the basal end, the tip of which is its narrowest 

 part. Its position is over the apical side of the spiral organ, 

 its axial zone being attached upon the vestibular lip of the spiral 

 limbus. Its widest portion spans over and projects beyond 

 the spiral organ to an extent of more than one-fourth of its 

 total width. Its narrowest part barelj^ spans the outer hair 



TABLE 1 



Giving in micra averages of the total width, the width of the attached axial zone 

 and the u'idth of the outspanning zone of the tectorial membrane of the adult hog 

 obtained from measurements, takenat the intervals of the coil specified, from jnedian 

 vertical sections of five cochleae and of six teased out membranes 



cells of the organ. Figures 1 to 4 are given to show its varying 

 proportions and its position. These four figures are drawings 

 to scale of the membrane and its environment as it appears 

 sectioned in one side of a median vertical section of the cochlea 

 of an adult pig. Thus the figures represent consecutively sec- 

 tions of the membrane across the 1st, 3rd, 5th and 7th half 

 turns of its coil. 



Measurements of the width of the membrane taken at the 

 above intervals of its coil from stained median vertical sections 

 of five different cochleae of the adult hog and measurements at 

 the same intervals of six membranes teased out from the adult 

 are recorded in table 1. Short segments of the long basal turn 



