THE MIDDLE EAR . 875 



3. The verticalis auriculae^ is a thin stratum of muscular and tendinous fibers 

 which extends upward on the convex surface of the concha from the eminentia 

 conchse. 



Actions. — The base of the concha is rounded and rests in a pad of fat (Corpus 

 adiposum auriculse), so that the movements of the external ear resemble those of 

 a ball-and-socket joint. It is noticeable that movements about the longitudinal 

 and transverse axes are accompanied by rotation. When the ear is vertical or 

 drawn forward ("pricked up"), the opening is usually directed forward ; conversely, 

 when the ears are "laid back," the opening faces backward. These movements 

 evidently result from the coordinated actions of several muscles which are very 

 complex and cannot be discussed in detail here. The scutularis acting as a whole 

 fixes the scutiform cartilage, so that the muscles which arise on the latter act 

 efficiently on the concha. The anterior auricular muscles in general erect the ear 

 and turn the opening forward. The interscutularis concurs in this action, causing 

 adduction and a symmetrical position of the ears; it also acts directly on the 

 conchal cartilage, since the scutulo-auricularis superficialis superior is in reality a 

 conchal insertion of the interscutularis. The scutulo-auricularis superficialis 

 accessorius draws the concha forward and turns the opening outward. The parieto- 

 auricularis adducts the concha and inclines it forward. The cervico-auricularis 

 superficialis is chiefly an adductor of the conchal cartilage, and directs the opening 

 outward. The cervico-auricularis profundus major turns the opening outward and, 

 acting with the parotido-auricularis, inclines the ear toward the poll. The cervico- 

 auricularis profundus minor tends to direct the opening downward and outward. 

 The parotido-auricularis draws the ear downward and backward, and acts with the 

 cervico-auricularis profundus major in "laying back the ears." The scutulo- 

 auricularis profundus major chiefly rotates the concha so that the opening is turned 

 backward. The scutulo-auricularis profundus minor assists in rotating the ear 

 so that the opening is directed forward. The tragicus shortens the external acoustic 

 meatus. The actions of the intrinsic muscles are inappreciable. 



Vessels and Nerves. — The arteries of the external ear are derived from the 

 anterior auricular branch of the superficial temporal, the posterior or great auricular 

 branch of the internal maxillary, and the anterior branch of the occipital artery. 

 The veins go chiefly to the jugular and superficial temporal veins. The nerves 

 to the muscles come from the auricular and auriculo-palpebral branches of the 

 facial nerve and from the first and second cervical nerves. The sensory nerves are 

 supplied by the superficial temporal branch of the mandibular nerve and the 

 auricular branch of the vagus. 



THE MIDDLE EAR 



The middle ear (Auris media) comprises the tympanic cavity and its contents, 

 the auditive or Eustachian tubes, and two remarkable diverticula of the latter, 

 which are termed the guttural pouches. 



The tympanic cavity (Cavum tympani) is a space in the tympanic and petrous 

 parts of the temporal bone situated between the membrana tympani and the in- 

 ternal ear. It is an air-cavity, which is lined by mucous membrane, and communi- 

 cates with the pharynx and the guttural pouches by the auditive or Eustachian 

 tubes. It contains a chain of auditory ossicles by which the vibrations of the 

 membrana tympani are transmitted to the internal ear. 



The cavity consists of: (1) A main part or atrium, which lies immediately to 

 the medial side of the membrana tympani; (2) the recessus epitympanicus, situated 

 above the level of the membrane and containing the upper part of the malleus 



1 EUenberger and Baum regard this as the homologue of the transversus and obliquus 

 auriculis of man. 



