1050 



ORGANS OF SPECIAL SENSE 



feriorly in the antitragus, from which it is separated by a slight depression, the pos- 

 terior auricular sulcus. The anthelix divides superiorly into two ridges, the 

 crura of the anthelix, and between these is a shallow depression, the triangular 

 fossa. The superior and dorsal margin of the auricle is rolled in towards the concha, 

 thus producing a prominent inturned rim, the helix, continuous anteriorly with the 

 cms of the helix, and interiorly with the lobule, and also an elongated depression, 

 the scapha (scaphoid fossa), which separates the helix and the anthelix. Superiorly 

 and dorsally the free margin of the helix frequently presents a slight projection, the 

 auricular tubercle (tubercle of Darwin) . Upon the medial surface of the auricle 

 the depressions of the lateral surface are represented by the eminence of the 

 concha, the eminence of the scapha, and the eminence of the triangular fossa ; 

 and the elevations by the fossa of the anthelix, transverse sulcus of the anthelix, 

 and the sulcus of the crus of the helix. The attachment of approximately one- 

 third of the medial surface covers up the two latter depressions. The cephalo- 

 auricular angle, which is formed between the dorsal free part and the side of the 

 head, averages 20 to 30 degrees. 



STRUCTURE OF THE AURICLE 



The characteristic features of the auricle just described are mainly produced by 

 a folded yellow elastic cartilage, the auricular cartilage, which, in addition to the 

 elevations and depressions already noted, presents the following additional features. 



Fio. 746. LATERAL AND MEDIAL SURFACE OF THE CARTILAGE OF THE RIGHT PINNA AND ITS 



MUSCLES, ETC. 



H3liois major Obliquua 



TransversuB 



Helicia minor 



Fibrous band 



completing fore 



part of meatus 



(NTITRAGO-HELICINE 

 FISSURE 



-TERMINAL INCISURE 



ISTHMUS 



Antitragicu; 



rraeicus SPIKE OF 

 LAMINA THAGI HELIX 



FISSURE OF SANTORINI 

 CARTILAGE OF MEATUS 



Projecting anteriorly from the helix near the crus is a small tubercle, spine of the he- 

 lix (fig. 746) ; a part of the helix, cauda helicis, is separated inferiorly from the anti- 

 tragus by _the deep antitrago-helicine fissure; and another deep fissure, the ter- 

 minal incisure, separates the cartilage of the auricle from that of the meatus, leaving 

 only a narrow strip, the isthmus, connecting the two. The cartilage of the tragus, 

 the lamina tragi, is separated from that of the auricle and is attached to the lateral 

 edge of the cartilage of the meatus. 



The skin of the auricle closely follows the irregularities of the cartilage. It is 

 tightly bound to the perichondrium of the lateral surface by the subcutaneous areolar 

 tissue, but much more loosely attached to the medial surface, and in the subcutaneous 

 tissue there is little fat except in the lobule, which is made up almost entirely of fat 

 and tough fibrous tissue. Hairs are abundant but rudimentary, except in the region 

 of the tragus and antitragus, where they may be large and long, particularly in males 

 and in the aged. Sebaceous glands are found on both surfaces, and are especially 

 well developed in the concha and triangular fossa, but sudoriferous glands are few 

 and scattered. 



