The iSTature of the Tectorial Membrane 175 



(8) A thin, exceedingly delicate, accessory tectorial membrane is de- 

 scribed lying along the under surface of the onter zone of the main 

 body to which its outer edge is lightly attached. It varies in width 

 somewhat as does the main body and its fibers extend inward toward 

 Hensen's stripe, but only extend over the outer series of hair cells. 



(9) To the several objections advanced by others to the assumption 

 that the basilar membrane performs resonant vibration, there is added 

 evidence that the basilar membrane is nothing more than a flat tendon 

 composed of a lamina of interconnected bundles of white fibrous con- 

 nective tissue whose purpose is merely to strengthen the floor of the 

 ductus cochlearis and the position of the organ of Corti, and which are 

 too rigid and firmly associated to allow of resonant vibration. And, 

 further, even if resonance were anatomically possible in the membrane, 

 the two layers of tissue on each of its sides would be sufficient to damp 

 such action. 



(10) To the evidence adduced that the different elements of the organ 

 of Corti are incapable of being moved separately by vibrations in the 

 basilar membrane, there is added evidence that the outer series of the 

 rods of Corti are especially so associated as to be incapable of separate 

 motion. The outer rods are more resistant to maceration than the 

 inner rods. 



(11) The theories in which the basilar membrane is considered the 

 vibrating mechanism in the cochlea are considered untenable, and an 

 application of the telephone theory to the tectorial membrane as the 

 vibrating mechanism is suggested on the basis of its logical position, its 

 extent, shape, proportions, consistency and structure, and the probable 

 character of the transformed and transferred sound waves in the endo- 

 lymph of the cochlea. 



BIBLIOGRAPHY. 



A VERS, Howard. Die Membrana tectoria — was sie ist, unci die Membrana 

 basilaris^ — was sie verrichtet. Anat. Anz., Bd. 6, 1891. 



Avers, Howard. On tTie Membrana basilaris, the Membrana tectoria, and 

 the Nerve Endings in the Human Ear. Zool. Bulletin, Vol. I, No. 6, 1898. 



Barth. Beitrag zur Anatomie der Schnecke. Anat. Anz., Bd. 4, No. 20, 1889. 



BoTTCHER, A. Ueber Entwicklungsgeschiehte und Bau des Gehorlabyrinthes. 

 Yerhandlungen der Kaiserl. Leop. Karol-deutschen Akad. der Xatur- 

 forscher., Bd. 35, 1869. 



