THE AUKICULA. 



829 



M. helicis major 



Spina helicis 

 M. helicis minor 



M. tragicus 



Fissure of 



Santorini 



Isthmus cartila- 



ginis auris 



Incisura terminalis 

 auris 



M. antitragicus 

 Fissura antitragohelicina 

 Cauda helicis 



FIG. 705. LATERAL SURFACE OP CARTILAGE OF THE 

 AURICULA (one-half natural size). 



Structure of the Auricula. The greater part of the auricula consists of a 

 lamella of yellow fibro-cartilage, the cartilage auriculae ; the cartilage is, however, 

 absent from the lobule, which is composed of fat and connective tissue. When 

 laid bare, the cartilage (Figs. 705, 

 706) presents, in an exaggerated 

 condition, all the inequalities of the 

 auricula, and is prolonged medially 

 to form a considerable portion of the 

 external acoustic meatus. The car- 

 tilage of the helix projects anteriorly 

 as a conical eminence, the spina 

 helicis, and its inferior extremity 

 extends downwards as a tail -like 

 process, the cauda helicis, which is 

 separated from the lower part of the 

 antitragus by the fissura antitrago- 

 helicina. The cartilage of the 

 auricula is continuous with that of 

 the meatus by a narrow isthmus, the 

 isthmus cartilaginis auris, measuring from 8 to 9 mm. in breadth. This isthmus corre- 

 sponds laterally with the deepest part of the incisura intertragica, and medially it 

 forms the outer boundary of a deep fissure, the incisura terminalis auris, which 

 separates the cartilage of the meatus from that of the concha. The upper edge of 

 the tragus fits into an angle below the crus helicis. Two fissures, in addition 

 to those already described, are usually present, one in the tragus and another 

 immediately behind the spina helicis. 



On the cranial surface of the cartilage (Fig. 706) the eminences produced by 

 the concha and fossa triangularis are separated by a transverse furrow, the sulcus 



antihelicis transversus, corresponding 

 with the crus antihelicis inferior; 

 further, the eminentia conchse is 

 crossed horizontally by a groove, the 

 sulcus cruris helicis, and almost vertic- 

 ally by a slight ridge, the ponticulus : 

 the latter indicates the attachment of 

 the m. auricularis posterior. 



Ligaments of the Auricula. The 

 cartilage of the auricle is attached 



termmalis o _ 



to the temporal bone by two fibrous 

 \cartiiageof bands which form its extrinsic liga- 

 ments, viz. : an anterior, stretching 



FIG. 706. MEDIAL SURFACE OF THE CARTILAGE OF from the zygomatic process to the spina 

 THE AURICULA (one-half natural size). helicis and tragus ; and a posterior, 



passing from the eminentia conchae 



and upper wall of the meatus to the mastoid portion of the temporal bone. Small 

 ligamentous bands pass between individual parts of the auricle, and form what are 

 termed its intrinsic ligaments. 



Muscles of the Auricula (Figs. 705, 706). The muscles of the auricle are 

 divided into two groups, extrinsic and intrinsic. The extrinsic muscles pass to the 

 auricula from the skull or the scalp, and are described in the section on Myology. 

 The intrinsic muscles, on the other hand, are confined to the auricula and are six 

 in number, four on its lateral and two on its cranial or medial surface. 

 (a) On the lateral surface (Fig. 705) 



1. M. helicis major passes upwards from the spina helicis along the ascending 

 part of the helix. 2. M. helicis minor covers the crus helicis. 3. M. tragicus, 

 quadrangular in shape, consists of fibres running vertically over the greater 

 part of the tragus. Some of its fibres are prolonged upwards to the spina helicis 

 and constitute the m. pyramidalis. 4. M. antitragicus covers the antitragus and 

 runs obliquely upwards and backwards as far as the antihelix and cauda helicis. 



M. transversus 



Ponticulus 



