Literary Notices. vii 



always located either at o° or i8o°; many individual variations occur. 



2. When sounds are produced on both sides in unsymmetrical 

 positions the results are inconstant. For any given point in either of 

 the two quadrants on one side of the median plane, a point can be 

 found m each of the two quadrants on the opposite side which in com- 

 bination with the first will give localization in the median plane at o° 

 or i8o°. 



3. For symmetrically placed sounds, one of which varied in in- 

 tensity by increasing the radial distance of the sounder, the subjective 

 sound passed from 0° or 180° to 90° right or left as the case might be. 



4. When both sounds are on one side in the horizontal plane the 

 resultant may be located either before or behind. When the sounds 

 are at 0° or 180° the resultant may be at 0° or 180°, usually at 0°, 

 but it is not true that weak sounds are preferably placed behind. 



5. When the attention was fixed on a given pomt and a single 

 sound was produced the latter was subjectively displaced in the direc- 

 tion of the point of fixation. 



6. When the muscles of one side are strained by voluntary effort 

 the result is a tendency to locate that side farther to the rear. 



7. When one ear has been fatigued by continued functioning no 

 influence was discovered in most cases on the localization. 



The authors conclude that these experiments (only part of which 

 are noted here) indicate that no conscious relation of the tones to either 

 ear exists, that sensations of touch play no part, that there is not a 

 judgement of the difference of intensities in the two ears. On the 

 other hand, many things show that sensations of movement are to be 

 regarded as the psychological basis of the auditory spacial perceptions. 

 It seems at first contradictory to deny the comparison of sound inten- 

 sities and yet appeal to discriminative motions which must be based 

 on such comparison, yet the authors believe that the difference in the 

 physiological excitation of the two ears conditions the motor impulses 

 with which the head reacts to the sound. These motor impulses 

 seem to form a rather superfluous Deus ex machina. In order to de- 

 termine whether the semi-circular canals contain the mechanism for 

 establishing the postulated reflexes, the whole apparatus was fastened 

 to a rotating disc. Sounds were usually displaced in the direction op- 

 posite to the rotation. If the eyes were closed and the sound was 

 produced after the rotation ceased the displacement was in the direc- 

 tion of the rotation. The displacement in other words, in both cases 

 was in the direction of the compensatory impulses to movements of the 

 head. 



