486 IRVING HARDESTY 



and the decrease in amplitude depends upon the tensity of the 

 tympanic muscles and also upon the pressure of the air in the 

 tympanic cavity. Thus it may be borne in mind that the 

 vibrations imparted to the lymph of the cochlea by the stapes 

 must correspond to the atmospheric waves but resemble them 

 only in frequency of vibrations and quality of vibration, for the 

 quality of the vibrations transferred to the endolymph must 

 depend upon the quality or form of the atmospheric vibrations 

 acting upon the tympanic membrane. 



The lumen of the scala vestibuli decreases in passing from the 

 base to the apex of the cochlea and that of the scala tympani 

 increases in passing from the apex to the base. The cochlear 

 duct increases in diameter in passmg to the apex where it ends 

 blindly. In the adult hog (fig. 4), the space on the apical side 

 of the spiral lamina, namely the scala vestibuli and cochlear duct 

 combined, increases in size in passing from base to apex. The 

 lumen of the scala tympani increases in passing basalward much 

 more than either or both the spaces on the apical side of the 

 spiral lamina, enlarging very greatly in its basal or longest 

 turn. These variations in the lumen of the lymph spaces must 

 result in variations in the resistance offered by their walls to the 

 vibratory motions passing from the base tow^ard the apex of the 

 cochlea. Waves passing apexward in the scala vestibuli are 

 thought to be imparted sunultaneously to the cochlear duct, the 

 vestibular membrane between being considered only to control 

 slightly or damp their force as affecting the tectorial membrane. 

 In the cochlea of the adult hog, there appears to occur in the 

 third turn of the coil a slight constriction of the scala vestibuli 

 (fig. 4). This seems present but less apparent in the adult beef 

 but not noticeable in the adult human and rat. No attempt 

 was made to reproduce it in the model, though when present 

 it must make an additional variation in resistance offered to 

 transmission of wave motion toward the apex. The coiled char- 

 acter of the walls of the cochlea must give complicated results 

 of resistance, some of them being no doubt phenomena due to 

 reflections of the vibratory motions. In the model no attempt 

 was made to reproduce the coil of the cochlea because of the 



