HEAD AND NECK OF THE HORSE 



27 



triimpet-shaped, with a large, oblique, elliptical opening bounded by 

 two free margins that meet at an angle at the apex of the pinna. 

 The cavity within the cartilage is at first of considerable spaciousness, 

 but, where the cartilage rests on the temporal muscle, a sudden nar- 

 rowing takes place, so that the deeper part forms a short and relatively 

 narrow tube. The lower part of the anterior free border splits into 

 two parts that form the foundation of the crura helicis of the undis- 

 sected ear. The anterior of these ends above in a pointed spina 

 helicis,^ while the posterior is the crista helicis. In the lower part 

 of the posterior border there is a notch {incisiira intertragica) that 

 separates a small projection, the antitragus, from a much more 



Conchal cartilage 



Antitragus. 

 Incisura intertragica.^ \ y/j/li 



Occipital bone. 



_ --Crista helicis. 



— Spina helicis. 

 Tragus. 



^-Scutulum. 



- Zgomatic process of 

 temporal bone. 



Styloid process. ' / / 

 Annular cartilage.' Postglenoid 



FiC4. 11. — The cartilages of the ear. 



definite and plate-like tragus.- From the lateral part of the deep 

 extremity of the conchal cartilage there projects a narrow pointed 

 styloid process. This overlies the annular cartilage, and is connected 

 with the wall of the diverticulum of the Eustachian tube by a short 

 band of fibrous tissue. Behind its root there is a foramen by which 

 the auricular branch of the vagus nerve gains the interior. 



The scutular cartilage (scutulum) ^ is a thin, curved plate, of 

 irregularly triangular outline, lying upon the temporal muscle anterior 

 to the broad base of the conchal cartilage. 



The [annular cartilage is in the form of a ring, incomplete 

 medially where its borders are connected by elastic tissue. It is 

 adherent to the margin of the external acoustic meatus of the 



1 c\i^ (helix) [Gr.], a coil. 



2 Tpdyoi (tragos) [Gr.], a goat (in allusion to the hairs growing on the tragus of 

 the human ear). 



■' Scutuhim (dim. of scutiim) [L.], a shield. 



