The I^ature of the Tectorial Membrane 137 



call}' useless for the purpose in mind, this preijaration was of interest 

 with reference to the position of Hensen's stripe. Cells and portions of 

 cells of the organ of Corti were adhering to the region involved, and, 

 in one place, nearly the whole organ, including both rods, for a stretch 

 of several cells. The ends of the hair cells could be distinguishel as such 

 by means of the crescentic lines of the exit of their hairs, and it could be 

 seen that the outer and inner rows of hair cells extended one on each 

 side of Hensen's stripe. In other words, both by actually distinguishing 

 it at times in their midst and by tracing it from the clean regions into 

 the region involved, it was evident that, in preparations of the pig fixed 

 in Zenker's fluid at least, Hensen's stripe lies between the inner and 

 outer rows of hair cells, and therefore over the relatively smooth line 

 occupied by the enclasped phalanges of the rods of Corti. 



It is difficult to say whether or not Hensen's stripe exists as a ridge 

 projecting beyond the general level of the under surface. A number 

 of investigators have described it as such; others, less definite, mention 

 it as a thickening or bunching of the material, and I remember none 

 to have specifically denied its being ridge-like. Sections should be 

 practically the only means by which this can be determined, but sec- 

 tions have proved very untrustworthy, because, even if a ridge is indi- 

 cated in them, one is never sure it is not due to inequalities of surface 

 shrinkage, and also because Hensen's stripe cannot be positively located 

 among the variable thickenings and markings that different sections 

 show. When viewed from the under surface, one gets a very decided 

 impression of a ridge, but, under magnification, allowing the whole 

 width of the membrane in the field, the greater part of the under sur- 

 face appears roof-like with Hensen's stripe as the highest part. Careful 

 focussing up and down under high power shows that the stripe is 

 higher than the adjacent surface, but much less so than was to be 

 expected, and that the roof-like appearance under low power was an 

 optical effect, explained as due to the ends of the fibers converging, 

 in the glassy matrix, from the two directions toward and into Hensen's 

 stripe. 



If the stripe runs along between the inner and outer rows of hair 

 cells, one might infer that it is a ridge which represents a strip of the 

 membrane never in contact with the projecting hairs, but which fits 

 into the groove walled on either side by the hairs, and that it should 

 have a width throughout corresponding to the width of the line of the 

 exposed surfaces of the phalanges of the rods of Corti. The exposed 



