DISSECTING MANUAL. 



furcates (crura antihelicis) above to enclose a depression 

 (fossa triangularis) . A process (tragus) overlaps the cavum 

 conchae in front; another (antitragus) overlaps it behind; a 

 notch (incisura intertragica) separates these processes; below 

 the notch is the lobule. Inner surface : This presents elevations 

 corresponding to the depressions on the outer surface, e.g., 

 eminentia conchae, etc. [743] 



Structure. A lamella of cartilage (cartilago auriculae) sup- 

 ports the greater part, except the lobule which consists of adi- 

 pose tissue; a narrow isthmus connects the cartilage inferiorly 

 with that of the meatus. The cartilage of the helix ends in 

 front and below in processes, the spina helicis and cauda 

 helicis respectively. Ligaments: The anterior runs from the 

 zygoma to the tragus and spina helicis; the posterior runs 

 from the mastoid process to the eminentia conchae and upper 

 wall of the meatus; the intrinsic ligaments are small bands 

 connecting individual parts. [745] 



Intrinsic Muscles. Outer surface: Helicis major, ascending 

 along the helix from the spina helicis. Helicis minor, cover- 

 ing the cms helicis. Tragicus, ascending over the tragus. 

 Antitragicus, ascending over the antitragus to the antihelix 

 and cauda helicis. Cranial surface: Transversus auriculae, 

 running from the eminentia conchae to the convexity of the 

 helix. Obliquus auriculae, crossing the furrow which corre- 

 sponds to the cms antihelicis inferior. [746] 



External Auditory Meatus. This is a canal, about an inch 

 long, which extends from the bottom of the concha to the ear 

 drum ; it is formed externally by fibro-cartilage and internally 

 by bone. It is S-shaped, narrowest (isthmus) near the drum, 

 and divided into the pars externa, which inclines inward, for- 

 ward, and slightly upward ; the pars media, the shortest, which 

 inclines inward and backward ; and the pars interna, the long- 

 est, which inclines inward, forward, and slightly downward. 

 Its inner end is almost circular, and is closed by the ear 

 drum. [746] 



[96] 



