296 THE CAT. [CHAP. ix. 



opening of the ear passage. It is deeply concave on the surface, 

 which is turned outwards and forwards, and convex on its inwardly 

 and backwardly-turned surface. It is hairy within and without, but 

 the hairs within are not numerous, though very long. Externally, 

 the pinna is covered with short hairs. Its inner surface presents 

 a variety of prominences and fossae, which aid in collecting and 

 concentrating the sonorous waves which impinge upon the organ. 



Immediately in front and externally, at the bottom of the external 

 opening, is a small rounded prominence, the tragus, and im- 

 mediately opposite it is a double prominence with an intervening 

 concavity, the anti-tragu*, into the concavity of which the .tragus 

 exactly fits. From the anti-tragus a low ridge runs upwards and 

 backwards to the margin of the pinna. A little further in, another 

 similar ridge runs (nearly parallel to that just mentioned) from the 

 margin of the pinna downwards to a very small prominence behind 

 the anti-tragus. Within and behind the tragus there is another 

 vertical undulating ridge, the post-tragus , while between its summit 

 and the tragus is a deep, rounded depression. 



Behind and above the summit of the post-tragus is the deepest 

 concavity of the concha, from the midst of which a singularly pro- 

 minent process, with a pedunculated appearance, projects inwards, 

 which process may be called the supra-tragus. A slight, short 

 ridge runs downwards and backwards from the lower margin of 

 the fossa in which the supra-tragus is placed. The cartilage of 

 the pinna is large and complexly-shaped, with a reduplication in 

 front. There is a reduplication of skin at the lower part of the 

 posterior margin of the pinna, producing a sort of pouch. 



The pinna is attached to two cylindrical cartilages, which follow 

 each other like two successive segments of a telescope, and form the 

 cartilaginous part of the meatus auditorius externus. 



A distinct body, called the scutiform cartilage, is only connected 

 with the pinna by ligaments, yet has muscles inserted into it which 

 indirectly move the ear. It lies on the temporal fossa just behind 

 the orbit, with its long axis antero-posterior, and enclosed in pre- 

 auricular aponeurosis. It can glide to and fro in the temporal 

 aponeurosis. 



The EXTERNAL AUDITORY MEATUS extends straight in from the 

 PINNA to the drum of the ear, or tympanic membrane. Its outer 

 part is formed by cartilage, the rest by bone, as has been before 

 described.* At its inner end the bony tube is grooved at its sides 

 and floor, and into this groove the tympanic membrane is fixed. 



The meatus is lined with mucous membrane, which is reflected 

 over the outer surface of the tympanum so as to form a coecal 

 mucous tube. In the bony part of the meatus this membrane is 

 thin, and closely adherent to the periosteum, but in its cartilaginous 

 part it is thicker, and bears hairs, together with sebaceous and 

 oleaginous glands. 



* Sec ante, p. 64, 



