416 SENSE-ORGANS /tND INTEGUMENT. 



culated process (//). This is really part of a transverse ridge, 

 extending craniocaudad on the medial wall of the auricular 

 cavity. This ridge is the antihelix (//) ; it divides the auricula 

 into a distal and a proximal portion. The portion distad of 

 the antihelix is the scapha (a); its surface is smooth except for 

 two slight longitudinal ridges extending distad from near the 

 two ends of the antihelix. That portion of the auricle that lies 

 proximad of the antihelix forms a deep irregular cavity known 

 as the concha (c). A deep furrow, corresponding to the anti- 

 helix, separates scapha from concha externally. The concha 

 extends caudad as a deep, rounded pocket; externally this 

 pocket forms a prominent convexity, the eminentia conchas 

 (/), on the caudal surface of the proximal portion of the 

 external ear. Farther proximad the concha narrows like a 

 funnel and becomes much compressed laterally, so that a sec- 

 tion of its cavity forms a narrow craniocaudal slit. 



The inner surface of the concha is marked by a number of 

 very prominent ridges and projections. These are usually due 

 to folds in the cartilage, so that external furrows and depres- 

 sions correspond to the internal projections. The edges of these 

 depressions serve for attachment of muscles (Fig. 169), by con- 

 traction of which the form of the concha is changed, the folds 

 of the cartilage thus serving as regions of greater flexibility. 



Two or three centimeters proximad of its external opening 

 the cartilage of the concha ends in a free edge which receives 

 within itself the distal end of the cartilaginous external auditory 

 meatus (Y). The two are united together by fibrous tissue. 

 The cartilaginous auditory meatus (/) extends as a nearly 

 cylindrical tube mediad and slightly craniad to the tympanic 

 membrane in the opening of the bulla tympani. This tube is 

 lined with integument which continues over the tympanic 

 membrane. The subcutaneous tissue of the tube contains the 

 ceruminous glands, which secrete the ear-wax and open on the 

 surface of the skin. 



To understand the relations of the muscles of the external 

 ear it is necessary to consider a little more fully the structure 

 of the auricular cartilage (Fig. 168), especially as compared 

 with the human ear. The ear of the cat differs from the human 



