354 THE FACULTY OF HEARING. 



of anticipated results. If we find divergence of structure and 

 function accompanied by corresponding change of physical sur- 

 rounding, our work and thought receive fresh motive in the hope 

 of discovering new links in the order of sensory function, or some 

 hitherto unknown combination of structural elements v/hich 

 suggests correction of current doctrine, or lends fresh significance 

 to accepted law. 



rf, on the contrary, the result of our examination goes 

 against the idea or expectation with which we set out, science 

 gains by the dismissal of the false tradition or fanciful hypo- 

 thesis whose ghost we have laid. But whatever be the result 

 of our work, the pleasure of pursuit is maintained by the 

 consciousness of a definite aim, and the endeavour to carry it 

 out with scientific method from a starting point based on scientific 

 premises. 



Many generalisations are included in the brief definition 

 of a '*' sensory organ.'' In the first place the animal possessing 

 .a sensory organ is brought thereby in direct relation with 

 external surrounding and influences 5 and this surrounding brings 

 with it many considerations of its varied nature and effects. 

 Thus, premising a distinction between special and general 

 sense we have to generalise concerning the particular physi- 

 cal influences of which particular organs are susceptible, 

 and also concerning the mode in which these organs are 

 played upon as instruments of the respective senses, e.g., light 

 undulations, and the optical properties of light which concern the 

 sense of sight ; vibrations of air, fluid, or solids, and the acoustic 

 properties which concern the sense of hearing, and so forth. Then 

 we have generalisations which connect this play of external physical 

 influences with the physical properties and condition of the tissues 

 and structural elements of the sensory organs as, ^,^., transparency 

 and refracting density for passage of light and formation of images, 

 elasticity for propagation of sound vibrations, (or vibrations un- 

 accompanied by sound) , &c. Again, in considering this association 



