CONDUCTION THROUGH OUTER EAR. 



601 



brane has no self-tone, and no succession of vibrations follows the 

 first effect of the sound waves. 



The existence of any special note of its own is prevented by 

 its conical shape, which is partly due to the traction of the handle 

 of the malleus. If a stretched membrane, such as that of a drum, 

 be drawn out at its centre so that it is no longer a flat surface, 



FIG. 234. 



Diagram of the tympauutn, showing tbe relation of the ossicles to the tympanic mem- 

 brane and the internal ear. The tympanum is cut through nearly transversely, and the 

 cavity viewed from the front (left ear). (Schafer.) m. t.. Membrane of the drum, to 

 which the handle of the malleus is attached at u m., head of malleus, which is held in 

 position by its suspensory ligament s.l.m., and external ligament l.e.m.; t., long process 

 of incus connecting malleus and st. stapes, the base of which closes oval opening of the 

 vestibule, e.au m., external auditory meat us. i.au.m., internal auditory meatus, where 

 the two parts of the auditory nerve enter, a and b. 



then its tension is different at the centre and the periphery, being, 

 of course, greatest at the point at which it is drawn upon, and 

 gradually decreasing toward the margin. Since the existence 

 of a tone of a definite pitch depends upon a certain degree of 

 tightness of the membrane, if no two parts of the membrane 

 have exactly the same degree of tightness, then, of course, no one 

 51 



