CHAP. XVIII.] THE EXTERNAL EAR. 67 



anterior curved extremity of the helix. The groove of the helix is 

 continued into the upper division, and the auditory canal leads from 

 the front and deepest part of the lower division, where it is over- 

 hung by the tragus and its protective tuft of hairs. The cartilage 

 of the pinna consists of one principal piece, from which that of the 

 tragus and antitragus is separated by a fissure filled up by fibrous 

 membrane. It is very flexible, and elastic, has a yellowish colour, 

 and belongs to the same category as the cartilages of the alse nasi, 

 &c. Ligamentous fibres bind the concha behind and above, and 

 the tragus in front to the bone and fascia in the neighbourhood. A 

 few muscular fibres passing between different parts of the auricle, 

 serve to impress upon them movements, but so slight as to be hardly 

 worthy of note. These fibres are found externally on the tragus, the 

 antitragus, the upper end of the helix, and behind on the concha. 

 The whole of the cartilaginous part of the ear is rendered moveable 

 by three muscles, the superior and anterior auris, arising from the 

 epicranial aponeurosis, and converging to the concha and helix, and 

 the posterior auris, passing between the mastoid process and concha. 



The auditory canal passes from the concha inwards for about an 

 inch, or rather more. It inclines a little forwards, and is slightly 

 bowed, so as to be higher near the middle than at either end. Its 

 width does not equal its height, and it is altogether narrower in the 

 middle. The membrana tympani, which terminates it, is placed 

 obliquely in consequence of the lower side of the meatus being longer 

 than the upper. The canal consists of two parts, a cartilaginous 

 and fibrous one, and an osseous. To form the first, the cartilage of 

 the concha and tragus is prolonged inwards as far as the auditory 

 process of the temporal bone, and constitutes a tube imperfect at 

 the upper and back part, where its deficiency is supplied by fibrous 

 membrane. This cartilage is rendered still further moveable by 

 partial slits in a vertical direction (incisurce Santorini). Muscular 

 fibres are described by some to exist in the meatus, which, accord- 

 ing to Haller, becomes shortened by their contraction. The osseous 

 part of the auditory canal consists in the foetus of a ring of bone, to 

 which the membrana tympani is attached (tympanic ring of the tem- 

 poral bone). In the adult, it is nearly three-quarters of an inch 

 long, and gives the meatus the form and direction already de- 

 scribed. 



The skin of the external ear is delicate, and well supplied with 

 vessels and nerves. The orifice of the meatus, besides being con- 

 cealed behind the tragus is defended by hairs, and a close arrange- 

 ment of ceruminous glands, which furnish an abundant secretion, 



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