CHAPTER XLIII. 



THE EAR. 



THE PINNA. THE TYMPANUM. 

 EXT. AUDITORY MEATUS. Otitis Media. 



Nerve Reflexes. Operations. 



Diseases. 



The Pinna is formed by elastic cartilage, with the ex- 

 ception of its lowest part, which is composed of fibro- 

 areolar and adipose tissue. The integument covering the 

 pinna is so closely attached to the underlying perichon- 

 drium that there is very little subcutaneous tissue be- 

 tween them, and the consequence is, that cold may easily 

 affect the circulation in the pinna, as seen in frost-bite, etc. 

 The different fossae forming the pinna are supposed to 

 concentrate the sound waves on the concha or entrance to 

 the external meatus, but experience has shown that, when 

 the pinna has been removed by operation or accident, the 

 interference with hearing is very slight. The nerves sup- 

 plying the cranial aspect of the pinna are : The auricularis 

 magnus, the posterior auricular, the small occipital, along 

 with Arnold's branch of the pneumogastric, while the 

 auriculo-temporal and the auricularis magnus supply the 

 outer surface. Disease of the upper cervical vertebrae, or 

 irritation of the cervical nerve in the neck from enlarged 

 glands, may cause pain to be felt in the pinna, through the 

 small occipital and the auricularis magnus referring it to 

 their auricular branches. 



The External Auditory Meatus is about one 

 and a quarter inches long, and consists of a car- 

 tilaginous portion about half an inch in length, and an 

 osseous portion about three-quarters of an inch in length. 

 The outer or cartilaginous portion is directed inwards and 

 slightly upwards and backwards, whereas the osseous 



