302 EXPERIMENTAL PHYSIOLOGY. 



(d.) Connect two telephones in circuit with a vibrating 

 Neef s hammer of an induction machine, and place a tele- 

 phone to each ear ; one hears the sound as if it came from 

 within one's own head in the vertical median plane. 



(e.) With a blindfolded person test his sense of the direc- 

 tion of sound e.g., by clicking two coins together. It is 

 very imperfect. Let a person press both auricles against 

 the side of the head, and hold both hands vertically in front 

 of each meatus. On a person making a sound in front, the 

 observed person will refer it to a position behind him. 



(f.) Test the highest audible sound by means of Galton's 

 whistle. 





