228 POPULAR SCIENCE MONTHLY. 



WHY IS THE HUMAN EAR IMMOBILE? 



By Dr. WALTER SMITH, 



LAKE FOREST COLLEGE. 



THE ear has had a varied history. The evolutionist has a remark- 

 able story to tell when he recounts the steps in the making of 

 this organ. He traces the opening of the ear to the gill-slits of the 

 fish forms of whose lineage we are. He shows (though this subject 

 concerns us less at present, and is still discussed with some uncertainty 

 as to details) how various structures in the region of this opening, 

 which had originally a different purpose, were modified to become the 

 series of little bones that propagate the vibrations of the air from the 

 tympanic membrane to the fluid of the inner ear. He shows further, 

 with greater or less completeness, how the cartilage shell grew on the 

 outer side of the head, and was supplied with muscles, so that it 

 could be moved about and even have its shape changed. 



To get a good illustration of the mobile ear we only need to watch 

 such an animal as the horse; the ear is as mobile as the eye, or more 

 so. The poet speaks of the horse's ear and eye as twinned; but it is 

 interesting to notice that each of the horse's ears can work independ- 

 ently. And it is evident that nature at one time meant, so to speak, 

 that man's progenitors should possess ears of similar mobility. She 

 gave them the projecting frame of cartilage and she attached to it the 

 muscles for its movement. Then in the course of the generations she 

 changed her mind and withdrew what she had bestowed. The carti- 

 lage shell, curiously wrought, is still there, and we regard it as add- 

 ing to the beauty of the head ; yet it is probably only a rudiment. The 

 tip of the ear, when present, is a small outgrowth on the outer fold 

 of the cartilage and is turned towards the center of the ear. The 

 muscles of the ear, seven in number, are also rudimentary. Occasion- 

 ally an individual is found who can move his ears; but even these 

 movements are generally of an abortive kind, and are so unusual that 

 the sight of them may distress those who are sensitive. 



Why has man lost this power? Is it simply a case of retro- 

 gression? Or is it a loss for the sake of a greater gain, possible 

 only through it? I think the reasons for this change in the organism 

 can be indicated; one can, at least, point with assurance to a great 

 mental gain in which it has resulted. 



It will prove helpful to an appreciation of this gain to inquire 

 first what man has lost in the passing of this mobility. The signifi- 



