George E. Shambaugh R47 
basilar membrane but are placed in contiguity, one with the other, thus 
forming a continuous whole, and that the thickness of the vibrating mem- 
brane is more accurately represented by a structure which includes the 
thickness of the fibers of the membrana basilaris plus the thickness of the 
superimposed cells as well (see Fig. 1). Again, the several radiating 
fibers of the membrana basilaris are not strung independently but they all 
form part of a continuous membrane and if thrown into vibration would 
not vibrate independently of the adjacent fibers. This fact, indeed, was 
recognized by Helmholtz and utilized in explaining the phenomena of 
Sea ices 
Additional evidence that this is not a vibrating membrane is found in 
the fact that the base of the inner rod of Corti rests on the firm structure 
of the labium tympanicum. This fact was recognized by Kuiles, who 
still retained the idea, however, that this is a vibrating membrane and 
explained that the vibrations take place about the base of the inner rod 
as a fulcrum, thus brushing the hair cells to and fro against the em- 
brana tectoria. 
In making a study of the structure of the membrana basilaris in the 
various parts of the cochlea, I have come across conditions which I believe 
demonstrate that this membrane cannot be the vibrating structure which 
it was believed to be by Helmholtz. In tracing the basilar membrane 
through carefully made sections near the beginning of the lower coil in 
the vestibule, I found that this membrane, at a considerable distance 
from the point where the cochlear tube begins, became so thick and rigid 
as to preclude any idea of its being a vibrating structure. ‘This is well 
shown in Fig. 1, which is taken from the labyrinth of a new-born pig. 
In a labyrinth taken from another pig, I found in this part of the cochlea 
complete absence of any structure that could properly be called a basilar 
membrane (see Fig. 2). Here the crista of the ligamentum spirale, as 
seen in a section, tapering gradually to a point, is attached directly to 
the labium tympanicum. ‘There is no basilar membrane and the perfectly 
formed organ of Corti rests on the stiff, rigid structure of the crista of the 
spiral ligament. In another preparation, a solid bony plate connected 
the lamina spiralis ossea with the outer wall of the cochlea at a point in 
the lower end of the basal coil where a perfectly formed organ of Corti 
was still present (see Fig. 3). The fact that the disappearance of the 
membrana basilaris as a possible vibrating structure takes place at a 
point in the lower end of the basal coil where the organ of Corti is still 
perfectly formed points to the conclusion that the vibration of this mem- 
brane is not essential for hearing. On the other hand, the fact that the 
