l6 UNIVERSITY OF MISSOURI STUDIES 



trudes from diametrically opposite sides of the bony wall of 

 the tube, on the left side more than on the right. But the 

 bone does not protrude far enough to actually cut off the 

 lower part of the tube from the upper. While, therefore, we 

 do not find a hard, inflexible partition, we find indeed some 

 kind of a partition since the space between the bony protru- 

 sions is filled with a delicate structure which we shall have 

 to study somewhat in detail. This structure, which we 

 shall always refer to hereafter as "the partition" in the 

 inner ear, is customarily spoken of under the name of its 

 discoverer as the organ of Corti. The lower part of this par- 

 tition has been shown to be a membrane, generally called the 

 basilar membrane. This is obviously the strongest part of 

 the partition, capable more than any of the other elements 

 of structure to resist a pressure of the fluid above or be- 

 low. But we must not think that this membrane is the main 

 part of the partition considering its volume. It is rather 

 small in bulk compared with the rest. Above the membrane 

 we see a triangular structure, something like two pillars which 

 have fallen towards each other. This structure is usually 

 called the rods of Corti. Its mechanical significance becomes 

 at once clear to us when we see at its sides the delicate end 

 organs of the auditory nerve fibres. These end organs would 

 obviously be crushed by the push of the fluid which occurs 

 now from above, now from below, as we have seen, if they 

 were not braced by this arch. No better protection could be 

 devised than this triangular structure which effectually pre- 

 serves the natural form of the soft tissues as the skeleton 

 does in the total animal body, without interfering with a 

 slight bending or compression of the tissues of the partition. 

 On the upper side of the partition, opposite the basilar mem- 

 brane, we notice another membrane, but much more delicate 

 in structure, easily torn to pieces when sections are made 

 for the miscroscope. This membrane touches the tufts of hairs 



