CHAPTEK XX. 

 DISEASES OF THE EAR. 



Foreign body in external auditory meatus. The difficulty 

 of extraction of foreign bodies from the external auditory meatus 

 depends partly upon the character of the body introduced, but 

 chiefly upon the anatomical peculiarities of the passage. 



The external auditory canal extends from the bottom of the 

 concha to the membrana tympani. It passes in a direction 

 inwards and somewhat forwards; its anterior wall is slightly 

 convex, whilst its floor presents a distinct elevation, which again 

 renders this portion of the passage convex. Owing to the 

 obliquity of the membrana tympani, the lower and anterior walls 

 of the canal are longer than the upper and posterior. 



The passage consists of two parts, an external shorter portion 

 composed of cartilage and an internal slightly longer portion 

 bounded by bone. By drawing the pinna upwards and backwards 

 the meatal canal can be made nearly straight a factor of some 

 importance in connection with the extraction of a foreign body 

 and with obtaining a clear view of the membrana tympani. The 

 length of the canal in the adult is about one and a quarter inches, 

 but it is proportionately shorter in the child. The diameter of 

 the canal naturally varies with age, but is also not quite uniform 

 in its whole length. Two constrictions can usually be demon- 

 strated, one in the cartilaginous portion near its junction with 

 the bony part, and the other a little external to the membrane. 

 Impaction of a foreign body beyond one of these constrictions con- 

 stitutes a real difficulty in extraction. This impaction may often 

 be aggravated by the swelling caused by the onset of inflamma- 

 tion. If a stream of water can be forced between the foreign body 

 and the wall of the meatus, the object can usually be driven out. 



