498 lEVING HARDESTY 



fenestra cochleae {FC) below it. These differences were probably- 

 unnecessary'. 



The external auditory meatus {EM, fig. 5, A) was represented 

 by a wide funnel made from block-tin. A wooden collar was 

 fitted upon the smaller end of this funnel that the tympanic 

 membrane could be stretched over it and secured more safely 

 and easily. For the tympanic membrane (TpM), a sheet of 

 that thin preparation of white fibrous connective tissue known 

 as 'Gold-beater's skin' was wet and stretched over the wooden 

 collar of the meatus and bound firmly about it with both twine 

 and rubber bands. The membrane became tense upon drying. 

 The collar was so trimmed that only its periphery was in contact 

 with the membrane, thus making the area of the vibratory part 

 of the membrane greater than the area of the circle formed by 

 the small end of the tin funnel. The area of this membrane 

 was about 30 times the area of the skin closing the opening 

 representing the fenestra vestibuli in the basal end of the model. 

 A tympanic membrane represented by sheet-rubber was found 

 useless in that it absorbed rather than transmitted its vibrations 

 to the ''ossicle" pressed against it. 



The ossicles of the middle ear were finally represented by a 

 piece of wood trimmed as shown in figure 7, B, and figure 5, A (0), 

 with an oval shaped piece attached to one end to serve as the 

 basis of the stapes {BS, fig. 7). At first pieces of hard wood 

 were cut and. joined together to imitate the three ossicles with 

 their joints and lever arrangement and with rubber bands for 

 the tensor tympani and stapedius muscles. This arrangement, 

 however, was found difficult to keep in place during the experi- 

 ments and it absorbed the vibrations of the tympanic membrane 

 considerably more than the single piece shaped as shown. Dur- 

 ing the experiments, a straight single piece was tried placed per- 

 pendicular to the center of the tympanic membrane and to the 

 membrane closing the fenestra vestibuli. This piece was of the 

 same thickness as that illustrated in the figures and its "basis 

 of the stapes" was similar, but its end representing the manu- 

 brium of the malleus was fan-shaped and was used extending in 

 both directions across the center of the tympanic membrane 



