THE HEAD AND NECK 1193 



lively soft in consistence. The prominent rim of the amicle is called 

 the helix. It is incurved, and commences at the upper and anterior 

 part of the concha in the cms helicis, already referred to. There- 

 after it surrounds the upper part of the anterior margin, and the 

 superior and posterior margins, of the auricle, and subsides below 

 in the back part of the lobule. In some cases the helix presents a 

 projection, called the tubercle of Darwin, which is situated on the 

 incurved margin, slightly above the level where the antihelix, to be 

 presently described, bifurcates into its crura. This projection is 

 well developed in the ears of quadrupeds, and forms the point or 

 tip. A short distance within the helix there is another curved 

 elevation, called the antihelix. This commences interiorly at the 

 back part of the antitragus and ascends behind the concha, above 

 which it divides into two diverging crura, upper and lower. 

 Between the helix and the antihelix is an elongated, narrow fossa, 

 called the fossa of the helix, or the scaphoid fossa, and between the 

 diverging crura of the antihelix there is a depression, called the 

 fossa of the antihelix, or the triangular fossa. 



The inner or cranial surface of the auricle presents convexities 

 corresponding to the fossae on the outer surface, the convexity 

 opposite the concha being especially prominent. 



Structure of the Auricle. — ^The auricle, with the exception of the lobule, is 

 composed of a plate of yellow elastic fibro-cartilage covered by skin. This 

 plate imparts firmness and elasticity to it, and is provided with hgaments 

 and intrinsic muscles. The skin is thin, and adheres closely to the fibro- 

 cartilaginous plate. It is provided with hairs, which are most plentiful in 

 the regions of the tragus and antitragus. The cartilage of the auricle is rolled 

 upon itself so as to form the outer or cartilaginous part of the meatus audi- 

 torius externus. This portion of it is attached internally to the external 

 auditory process of the temporal bone by fibrous tissue. The rolled or 

 tubular portion presents a deficiency at the anterior and upper part, between 

 the tragus and the commencement of the helix, which is occupied by a fibrous 

 membrane. It also presents a variable number of transverse clefts, called 

 the fissures of Santorini, which are filled with fibrous tissue. The lower ex- 

 tremity of the cartilage of the helix is separated from the cartilage of the 

 antiheUx by a deep cleft. The part of the cartilage of the heUx behind this 

 cleft is known as the processus caudatus helicis. At the upper and anterior 

 part of the auricle, where the helix begins to curve backwards, the cartilage 

 presents a small sharp projection, called the spine of the helix. 



Ligaments of the Auricle. — These are two in number, anterior 

 and posterior. The anterior ligament extends from the spine of 

 the helix to the z\goma of the temporal bone close to its root. 

 The posterior ligament extends from the cranial aspect of the 

 concha, under cover of the retrahens auriculam muscle, to the 

 mastoid process. 



Intrinsic Muscles. — These muscles, which are very thin and pale, 

 are confined to the auricle and are six in number, four being situated 

 on the outer surface, and two on the inner surface. 



Muscles on Outer Surface. — These are as follows : (i) the musculus 

 helicis major; (2) the musculus helicis minor; (3) the musculus 

 tragicus ; and (4) the musculus antitragicus. 



