1484 



HUMAN ANATOMY. 



THE EXTERNAL EAR. 



The external ear, the outermost subdivision of the auditory organ, includes 

 (i) the auricle, the funnel-shaped appendage attached to the side of the head for the 

 collection of the sound-waves, and (2) the external ixiiditory canal, which conveys 

 these stimuli to* the tympanic membrane, the flexible partition closing the canal and 

 separating it from the middle portion of the ear. 



Fossa helici? 



The Auricle. 



The auricle (auricula), also called the/>z«;z«, is attached to the side of the head 

 around the opening of the external auditory canal, midway between the forehead and 

 the occiput. It presents two surfaces, an external and an internal. The angle which 

 its internal surface forms with the head, the cephalo-auricular angle, is usually about 

 30°, but varies from 20-45®. The circumference of the auricle is somewhat pyriform 

 in outline, with the broadest part of the figure above. The external surface of the 

 auricle is irregularly concave and presents for examination several well-marked 

 depressions and elevations, which depend, for the most part, upon the corresponding 

 modelling of the underlying cartilage. The concha, the largest and deepest of the 

 concavities, surrounds the entrance or meatus to the external auditory canal. This 

 funnel-like fossa is subdivided by an obliquely transverse ridge, the crus helicis, 

 continuous with the helix, into the upper and smaller part, the cymba con- 

 chse, and a lower and larger part, the concha proper or cavum conchae. The 



tragus is an irregular 

 Fig. 1243. eminence in front of, and 



slightly overlapping, the 

 meatus. At the upper 

 extremity of the tragus, 

 just below a notch, the 

 incisura anterior, that 

 separates the tragus from 

 the upper part of the 

 auricle, is sometimes seen 

 a small elevation, the 

 tuberculum supratrag- 

 icum. The antitragus 

 is an eminence behind the 

 tragus and separated from 

 it by a deep notch, the 

 incisura intertragica. 

 The lobule contributes 

 the rounded lower ex- 

 tremity of the auricle. In 

 contrast to other parts of the pinna, it possesses no framework of cartilage and, hence, 

 is soft and inelastic. The helix forms the scroll-like margin of the ear, sweeping from 

 the upper part of the tragus in front to the lobule behind. It is more or less rolled 

 upon itself so that its margin looks forward. On the anterior edge of the helix, near 

 the junction of its upper and middle thirds, is sometimes found a small triangular ele- 

 vation, the car-point or tubercle of Darwin, which is of interest as representing, ac- 

 cording to the last-named authority, the erect pointed extremity in the expanded ears 

 of certain quadrupeds. It is said to be constant in the foetus of about the sixth month 

 and to be more common in the male than in the female. In front of and parallel to 

 the helix, is a curved vdge, the antihelix which begins at the antitragus below, 

 forms the concave posterior boundary of the concha, and divides above it into a 

 superior and an inferior crus between which lies the fossa of the antihelix or the 

 fossa triangularis. A narrow groove between the helix and the antihelix marks 

 the fossa of the helix or the scaphoid fossa. 



The elevations on the external surface of the auricle are represented by 

 depressions on the cranial surface, and conversely the depressions on the external 



Right auricle, outer aspect. 



