552 



ORGAN OF HEARING. 



ear, it will widen and straighten the auditory 

 passage. 



The retractor or posterior muscles of the ear, 

 ( M. retrahentes avriculam, s. posteriores auri- 

 cula.) These ordinarily consist of three bundles, 

 sometimes only two, which, taking their origin 

 from the mastoid process, run forwards to the 

 cartilage of the ear, into which they are inserted 

 at the eminence on the back of the concha, 

 corresponding to the commencement of the helix 

 on the other side. 



In drawing the ear backwaids, these muscles 

 w il dilate and flatten the concha, and widen 

 the entrance to the auditory passage. 



The anterior muscle oj the ear, ( M. attrahens 

 auriculam s. anterior auricula,) arises from the 

 zygomatic process, and, in its course backwards 

 to the ear, gradually contracts, until it ends in a 

 short tendon, which is inserted into the anterior 

 surface of the helix, immediately above the 

 tragus. It draws the ear forwards. 



Fig. 255. 



where the helix rises from the concha, and is 

 inserted into the posterior margin of the ascend- 

 ing portion of the helix. 



The muscle of the tragus, Cm. tragicus). Of 

 an oblong square form, this muscle covers the 

 outer surface of the tragus, from the lower part 

 to the upper margin of which its fibres run. 



The muscle of the antitragtu, (m. antitragi- 

 cus). The fibres of this muscle arise from the 

 outer surface of the antitragus, and are inserted 

 by a small tendon to which they converge into 

 the lower extremity of the anthelix. 

 Fig. 256. 



a. m. helicis major; 



c. m. helicis minor ; 



d. m tragicus ; e. m. 

 antitragicus. 



The intrinsic muscles situated on the concave side of 

 the auricle (diminished). (From Soemmerring ). 



The transverse muscle of the ear, (m. trans- 

 versus auricula,) is situated on the back of the 

 ear. It is composed of fasciculi not very dis- 

 tinctly muscular, which run from the dorsum of 

 the concha to the back of the anthelix, and the 

 elevation which corresponds to the navicular 

 fossa. 



Fig. 257. 



a. transversus mus- 

 cle ; b. helix ; c. back 

 of the concha ; d. tra- 

 gus; e. fissure of Saa- 

 torini. 



The cartilage of the left auricle from behind, and 

 the extrinsic muscles (diminished). (From Soemmer- 

 ring). 



a. m. attollens auriculam ; 6. m. anterior auri- 

 culae ; c. d. two m. retrahentes auriculam. 



Intrinsic muscles of the ear. These muscles 

 are very delicate and weak, little adapted to 

 produce any sensible change in the form of the 

 ear. Five are admitted : 



The larger muscle of the helix, (M. helicis 

 major,) arises from the lower arid anterior part 

 of the helix, on the outer and anterior surface 

 of which it ascends for about three quarters of 

 an inch, and then is inserted into the helix above 

 the point where the ear becomes free from its 

 attachment to the head. 



The smaller muscle of the helix, (M. helicis 

 minor.) This lies farther down and more be- 

 hind than the preceding. It begins at the place 



The back of the cartilage of the' external ear and 

 the transversus muscle (diminished), ( From Soemmer- 

 ring). 



E. The external auditory passage, (meatus au- 

 ditor ius externus s. porus acusticus; Fr. Le con- 

 duit audit if ou auriculaire; Germ. Der Gehur- 

 gang.) Like the Eustachian tube, the external 

 auditory passage is composed of an osseous 

 portion, and a portion partly cartilaginous and 

 partly membraneous. The osseous portion has 

 been already described as a part of the outer 

 wall of the tympanum; the other portion comes 

 to be noticed here as a continuation of the car- 

 tilage of the auricle. The passage will then be 

 considered as a whole. 



Cartilaginous and membraneous portion of 

 the external auditory passage, meatus auditorius 

 cartilagineus-membranaceus. This portion of 

 the auditory passage, about half an inch long, is 

 formed in front and below by cartilage, above 



