Do We Hear Sound f 3 



vious paragraph, may the ear be compared with the fa- 

 miliar recording phonograph! 



The general picture of the ear apparatus is well known. 

 The drum membrane lies in the depth of the external 

 auditory canal. The small ear ossicles, malleus, incus 

 and stapes, are familiar to every high school student of 

 physiology. Further we probably remember that the end 

 organ of hearing, the organ of Corti, lies immersed in the 

 liquid of the inner ear contained within a cavity of the 

 temporal bone. The bony container has two openings in 

 it which are related to the middle ear cavity. The foot- 

 plate of the stapes occupies the oval window while the 

 smaller round window is provided with a membranous 

 diaphragm. The malleus is attached to the drum mem- 

 brane and is brought into relation with the stapes 

 through the intermediate incus. The drum membrane in 

 this manner comes to have a definite connection to the 

 liquid of the inner ear. 



May the mechanics of hearing be likened to the fa- 

 miliar lateral-type recording phonograph? The dia- 

 phragm of the phonograph corresponds to the drum mem- 

 brane; the hinged stylus may be likened to the hinged 

 ossicles; the groove on the recording plate may be com- 

 pared to the liquid of the inner ear. The sound pulses 

 strike the phonograph membrane and cause it to swing 

 in-and-out. The stylus membrane acts like a lever — the 

 long arm from the center of the diaphragm to the ful- 

 crum; the short arm resting a pointed tip in the wax. 

 The excursion of the shorter arm is necessarily less than 

 that of the longer arm and its power is thereby in- 

 creased. We know that this record when placed on a 

 reproducing phonograph will yield in a general way the 

 cause — the voice or the instrument. Just so all modern 

 theories of hearing assume that the sound pulses cause 

 an in-and-out swing of the drum membrane. The lateral 

 motions are transferred to the hinged ossicles; the long 



