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HUMAN PHYSIOLOGY 



also a contact between some of the material and our 

 receptors, but our thought is of the main mass of the 

 substance which may be far away. Hearing and vision 

 are distinguished from the other senses and superior 

 to them in that it is not matter but energy which comes 

 to us from the sources of stimulation. The ear and the 

 eye are called distance receptors. Through them our 

 universe becomes greatly enlarged. 



FIG. 36. Semi-diagrammatic section through the right ear; G, 

 external auditory meatus; T, membrana tympani;P, tympanic cavity; 

 o, fenestra ovalis; r, fenestra rotunda; B, semicircular canal; S, cochlea; 

 Vt, scala vestibuli; Pt, scala tympani; E, Eustachian tube. (Czermak.) 



We have seen that the mechanisms of the internal 

 ear are useful to a great degree in connection with the 

 maintenance of equilibrium. In some animals this is 

 probably their essential function. It is not hard to see 

 that organs sensitive to displacements of the body as 

 a whole might also become responsive to the slight and 

 repeated shocks which we call sound waves. In the 

 higher forms, including ourselves, there is a definite 

 division of the labyrinth to provide for the two services. 



