No. I.] THE VERTEBRATE EAR. 303 



attention to my newspaper favored my dozing into semicon- 

 sciousness, from which I was suddenly startled by what at first 

 seemed to be a sharp blow upon the newspaper in front of me, 

 but before I could open my eyes I was perfectly conscious that 

 this was an illusion, and that the paper had not been struck and 

 had not given forth the sound. This was confirmed by seeing 

 the conductor coming from near the door, which he had just 

 slammed, and by finding my paper in its former position. Now 

 the sense organs whose attention had been last directed to the 

 outer world were the eyes, and the stimulus entering the brain 

 through the ears was referred to their field of vision, but the 

 stimulation of the auditory centre had been so keen that the 

 distinctive qualities of the sound of a slamming door at once 

 corrected the illusion that it was the paper which had given 

 forth the sound, notwithstanding the fact that the first impres- 

 sion had all the distinctive qualities of a sharp blow upon the 

 paper. In this instance the timbre or tonal qualitatives distinc- 

 tive of the slamming door were for the instant suppressed by 

 the state of the co-ordinating mechanism, though they were 

 soon recognized. We have to go but a step further to recog- 

 nize that such internal modifications may become permanent. 



The auditory perceptions are largely dependent upon educa- 

 tion. This is true of the results of all sound stimuli; thus, in 

 the young child possessing auditory organs structurally per- 

 fected, as far as the microscope reveals, we find a great lack of 

 the "proper" appreciation of sounds and tonal compositions, — 

 a lack due to small experience, i.e. to a lack of co-ordinat- 

 ing powers in the central nervous system. We depend for 

 our judgments of the direction on the constant relation main- 

 tained between the external ear and the auditory meatus to the 

 surrounding air, and we are very liable to false judgments on 

 any alteration of the normal relation. If, for instance, the hand 

 or other solid body be placed close to the side of the head and 

 in front of the ear, the entrance of sound waves is modified 

 much as it would be were the external ear to be revolved about 

 the meatus as an axis, and hence the sound waves make their 

 way in from behind with greater facility than from in front. 



We are greatly assisted in recognizing the direction of sound 

 by the position of the external ear on the side of the head, 

 since it renders the perceptions of sounds of like intensity 



