THE COMPARATIVE ANATOMY OF THE 

 INTERNAL EAR IN VERTEBRATES 



By R. H. BURNE 



Every one is familiar with the streak, known as the lateral line, 

 upon the sides of fishes ; it can be observed any day upon the 

 fishmonger's slab. But it is perhaps not so universally known, 

 though a matter of common knowledge to any one at all 

 acquainted with comparative anatomy, that this line and 

 similar ones upon the head and face shelter a series of 

 cutaneous sense organs, of simple structure but Ainfortunately 

 at present of enigmatical function, known collectively as the 

 '■ organs of the lateral line." 



In all probability it is in this system of sense organs of the 

 skin, peculiar to aquatic vertebrates, that we must look for the 

 birthplace of the ear. For in the first place, we have some 

 evidence l of a rough similarity in function between the two ; 

 in the second, there are certain anatomical peculiarities, 2 par- 

 ticularly of the nerve supply, that indicate beyond all reasonable 

 question that the ear and the lateral-line organs belong to one 

 and the same sensory system and that the ear is only a lateral- 

 line sense organ specially set apart and so refined as to act, in the 

 first place, as an equilibrating organ for recording alterations 

 in the position of the body ; in the second, though possibly 

 only among terrestrial vertebrates, as an auditory organ 

 sensitive to vibrations of the surrounding medium too subtle 

 to be felt by the sense organs of the skin. 



In this article an attempt is made to give a general idea of 

 our present knowledge, based upon the work of Retzius, 3 of the 

 more important changes of structure that have accompanied 

 this elaboration and refinement of function. 



To grasp the significance of the individual steps in the 

 process — for often the changes are in themselves insignificant — 



1 Parker, Bull. Bureau Fisheries, 24, 1904, p. 185. 



1 Beard, Zool. Anz. vii. 1884, p. 142 ; Ayers, Jour. Morfih. vi. 1892, p. 1. 

 5 Retzius, Das Gehbrorgan der Wtrbelthiere, Stockholm, 1881-4. 



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