94, 



DEVELOPMENT OF THE EAR. 



The embryonic tympanic membrane is at first close to the exterior, the external 

 meatus being scarcely existent, although the several parts of the external ear are very 



Fig. 109. SKETCHES SHOWING THE GRADUAL DEVELOPMENT OF THE PARTS OP THE EXTERNAL EAR 



FROM PROMINENCES UPON THE MANDIBULAR AND HYOIDEAN VISCERAL ARCHES. (His.) Variously 



magnified. 



F is an outline sketch showing the several parts of a well-developed adult ear, Ird natural size. 



1, 2, prominences on the mandibular arch ; 3, prominence between the two arches, immediately 

 over the cleft, prolonged posteriorly into c, behind the hyoidean arch ; 4, 5, and 6, prominences on the 

 hyoidean arch ; L, in B. otic vesicle (seen also in A) ; K, lower jaw. 



Of the prominences enumerated 1 forms the tragus ; 2, 3, and 3c, the helix ; 4, the autihelix ; 

 5, the antitragus ; and 6, the lobule (vide F). 



