THE SENSE OF HEARING 149 



and learning to use it. Crying, speaking, handling, the child learns, not exp(;ri- 

 mentally and with any purpose of the will, by setting in motion the muscles of 

 the throat and thorax, the arm and the hand, to try the effect and benefit which 

 may result. The soul never arrives at a direct perception of these special mem- 

 bers, not to say that the knowledge of their existence and of the means of setting 

 them in motion would be the prerequisite incitement to their use. That primary 

 incitement consists much more in the activity of the muscles themselves ; the 

 child cries at first mechanically — that is to say, its vocal muscles are thrown 

 into action in a reflex w^ay, the muscular irritation being the effect of the irrita- 

 tion of the nerves of sensation in the brain produced by an external object. 

 With this activity is connected a determinate, and for every muscle a specific 

 feeling, a so-called muscular feeling, of which the child becomes conscious, as it 

 does at the same time of the sensation of sound which is the result of the activity 

 of the vocal njuscles. Thus the child first learns that this specific muscular 

 feeling always coincides with that sensation of sound, or, again, that with the 

 muscular feeling which the movement of the arm produces, is associated a sen- 

 sation of pressure when the limb encounters an external object, which object 

 may at the same time give rise to a visual sensation, &c. The education of the 

 soul thus proceeds step by step, and in this way it very gradually succeeds in 

 obtaining an indelible idea of all possible combinations of the muscular feelings, 

 and in understanding their signification from the consequences experienced, so 

 that it knows exactly what sort and degree of effort the will must make, in order 

 to call forth any definite muscular feeling, and attain the results known to be 

 associated with it. The same circuitous process would lead to the conscious use 

 of the muscles of the ear if their unconscious reflex activity were at first possi- 

 ble, for this would be our instructor by means of the associated muscular feeling 

 and the knowledge of its consequences. Respecting this, however, it is enough 

 to say that the detriment occasioned by the defect of motion is not great, since 

 the human head is in the highest degree movable in all directions, and hence we 

 can well dispense with any movement of the eai'S. The purposes connected 

 with a change of position of the ears will presently be noticed. 



If we ask now what function the outer ear fulfils, in what acoustical relation 

 it stands to the air-wave, the common answer is at hand : to intercept and r<i- 

 ceive it; but this is by no means an exhaustive explanation. It is true, indeed, 

 that this member is an auxiliary but not an altogether indispensable part of the 

 auditory apparatus, since it is well known that, where it is wanting, not only 

 does the perception of sound exist, but that often it is not sensibly weakened 

 or affected. The same is the case if the external ear be occluded by filling its 

 cavity with some pulpy inelastic substance, while the auditory canal, and that 

 alone, is kept open for the transmission of sound by the insertion of a small 

 tube. But although the auricle is not indispensable, it is not in vain that it oc- 

 cupies its place. Its design may be sought in a two-fold relation to the sound- 

 producing waves of the air: these may rebound against it, as the light is re- 

 flected from a mirror, and by means of its different eminences and depressions 

 be thrown in greater quantity into the interior passages ; or it may serve as a 

 sort of sounding-board, or, more correctly, as the bridge of a violin — that is to 

 say, i-eceiving the wave of sound and, being a rigid, elastic, outstretched carti- 

 lage, it may itself be throwar into vibration, and through the walls of the auditory 

 canal communicate that vibration to the tympanum, as the bridge of the violin 

 transmits. the vibrations of the strings to the sounding-board. In both cases 

 the advantage w^onld consist in economizing a part of the air-wave which would 

 otherwise be lost. It was usual, formerly, to seek in the action first mentioned, 

 the reflection, namely, of the wave into the auditory passage, the service of the 

 outer ear. By more careful consideration, however, of the directions in which, 

 according to physical laws, waves of sound, striking in different lines upon its 

 differently shaped parts, must be reflected, the auricle is shown to be very little 



