THE FACULTY OF HEARING. ^^^ 



the requirements of external surrounding and internal sense, it is 

 necessary to study the extreme limits of modification and the 

 possible exclusion of non-essential parts, within which the struc- 

 tures may still be recognised as an instrument of hearing. In a 

 word, the scientific aspect of the subject brings us in immediate 

 contact with the most difficult problems of structural development, 

 and the physiology of the senses. But as the anatomical character- 

 istics of a complex sensory organ explain themselves only to those 

 who have already studied each known type of construction, while 

 the due estimation of sensory function requires an equally wide 

 grasp of physiological law, I fear that I should fail to make myself 

 understood if I attempted to describe this tympanal structure in its 

 minute details, or to discuss, over each detail, the principles on 

 which every surmise regarding its functional significance must be 

 tested and determined. 



The middle course upon which I hope to have alighted, and 

 which appears to me most suitable, is to preface our special 

 subject with a brief consideration of the essential characteristics of 

 an auditory sense, and of the structural elements which are essential 

 to an organ of hearings and finally of the rationale of those 

 diversities of structure which seem to indicate variations of type 

 of the several sensory organs. In thus placing before my hearers the 

 general issue as well as the particular case, at the same time avoiding a 

 too rigorous form and phrase of science, I hope to win for my subject 

 that interest which it might not otherwise possess. Be this as it 

 may, there is an undoubted advantage in keeping in view what has 

 been already done in any line of enquiry, when studying any fresh 

 point or new instance which promises important addition to our 

 knowledge. For nothing sharpens our power of observation so 

 much as the knowing what to look f or j nothing quickens our 

 interest more powerfully than the direction of our vision beyond 

 the immediate confines of the known. Thus if in any enquiry 

 which we undertake we find as we proceed a true accordance of 

 the new with the old, our labour lightens with each confirmation 



