George E. Shambaugh 251 
membrane possesses is its lamellar structure. An immense number of 
delicate lamelle are found taking their origin from the portion of 
the membrane which rests on the labium vestibulare. The lamellz, 
more compact where they converge along the dorsum of the membrane, 
curve gracefully outward and downward towards the lower border of the 
membrane. These lamellae give the membrana tectoria somewhat the 
appearance of a soft feather. They vary in length with the varying 
size of the tectorial membrane, the shorter lamelle occurring near the 
beginning of the basal coil, and the longest at the apex of the cochlea. 
They are supported and held together by an apparently homogeneous 
semi-fluid substance. The specific gravity of this substance appears to be 
the same as that of the endolymph in which the membrane is suspended. 
This is shown by the fact that, in spite of its semi-fluid character, it re- 
tains its position in the endolymph though supported only by its contact 
with the labium vestibulare and where the “ Streifen of Hensen” is in 
contact with the supporting cells of the organ of Corti. The use of hard- 
ening and fixing agents always produces decided distortions of the mem- 
brana tectoria as the result of shrinking. This shrinking is not evenly 
distributed throughout the membrane but varies evidently owing to the 
unequal distribution of the lamelle. The most marked shrinking taking 
place where the lamellz are the most compact, that is, along the dorsum 
of the membrane and toward the end which is attached to the labium 
vestibulare. ‘This results in a certain more or less characteristic distor- 
tion of the membrana tectoria which is often observed in our best prepa- 
rations otherwise free from distortions. This characteristic distortion 
is the pulling of the membrana tectoria back towards its attachment at 
the labium vestibulare, and away from the hair cells. The result is 
that often in otherwise perfect preparations the membrana tectoria does 
not he in contact with the hair cells but is lifted up and pulled back 
toward the modiolus. 
These characteristics of the membrana tectoria render it suitable to 
respond to the most delicate impulses passing through he endolymph. 
The great variation in size of the membrane from one end of the cochlea 
to the other, together with its lamellar structure, are physical character- 
istics which suggest the probable basis for a series of resonators which 
make it possible for the membrane in one part of the cochlea to respond 
to impulses of a certain pitch and in another part to impulses of another 
pitch. In this way the small impulses produced by the high pitched 
tones would in some way set to vibrating the tiny tectorial membrane 
found in the beginning of the basal coil, while the larger impulses arising 
