EXTERNAL AUDITORY CANAL. 743 



The muscle of the tragus (m. tragicus) is a flat bundle of short fibres 

 covering the outer surface of the tragus : its direction is nearly vertical. 



The muscle of the antitragus (in. autitragicus) is placed obliquely over the 

 antitragus and behind the lower part of the antihelix. It is fixed at one 

 end to the antitragus, from which point its fibres ascend to be inserted into 

 the tail-like extremity 'of the helix, above and behind the lobule. 



The transverse muscle (m. transversus auriculas) lies on the inner or cranial 

 surface of the pinna, and consists of radiating fibres which extend from the 

 back of the concha to the prominence which corresponds with the groove of 

 the helix. 



The oblique muscle (Tod) consists of a few fibres stretching from the back 

 of the concha to the convexity directly above it, across the back of the 

 inferior branch of the antihelix, and near the fibres of the transverse muscle. 



Arteries r>f the pinna. The posterior auricular artery, a branch from the external 

 carotid, is distributed chiefly on the posterior or inner surface, but sends small branches 

 round and through the cartilage to ramify on the outer surface of the pinna. Besides 

 this artery, the auricle receives others, the anterior auricular from the temporal in 

 front, and a small artery from the occipital behind. 



The vei)is correspond much in their course with the arteries. They join the tem- 

 poral vein, and their blood is returned therefore through the external jugular. 



Nerves of the pinna. The great auricular nerve (p. 638), from the cervical plexus, sup- 

 plies the greater part of the back of the auricle, and sends small filaments with the pos- 

 terior auricular artery to the outer surface of the lobule and the part of the ear above it. 

 The posterior auricular nerve, derived from the facial (p. 612), after communicating with 

 the auricular branch of the pneumogastric, ramifies on the back of the ear and supplies 

 the retrahent muscle. The upper muscles of the auricle receive their supply from the 

 temporal branches of the same nerve. The auriculo-temporal branch of the third 

 division of the fifth nerve (p. 606) gives filaments chiefly to the outer and anterior 

 surface of the pinna. 



THE EXTERNAL AUDITORY CANAL. 



The external auditory canal (meatus auditorius externus) extends from 

 the bottom of the concha to the membrane of the tympanum, and serves to 

 convey to the middle chamber of the ear the vibrations of sound collected 

 by the auricle. The canal is about one inch and a quarter in length. In 



Fig. 499. VIEW OP THE LOWER HALF OF THE Fig. 499. 



AURICLE AND MEATUS IN THE LEFT EAR 



DIVIDED BY A HORIZONTAL SECTION (after 



Sommerring). 



1 and 2, cut surfaces of the bony part of the 

 meatus ; 3, cut surface of the cartilage of the 

 pinna ; 4, external meatus with the openings of 

 numerous ceruininous glands indicated ; 5, lobule ; 

 6, membrane of the tympanum j 7, dura mater 

 lining the skull. 



its inward course it is inclined somewhat 

 forwards ; and it presents likewise a dis- 

 tinct vertical curve, being directed at fir^t 

 somewhat upwards, and afterwards turning 

 somewhat abruptly over a convexity of 

 the osseous part of its floor, and dipping 



downwards to its termination, a change of direction which must be 

 borne in mind by the surgeon in introducing specula into the ear. The 



