164 THE ANATOMY OF THE HORSE. 



soon as the ear is finished. On one side the muscles and cartilages of 

 the ear may be dissected ; and then the other side may be denuded of 

 skin in the same manner as the first, in order to follow the vessels and 

 nerves. 



Muscles of the Ear. — These are divided into extrinsic and intrinsic. 

 The former have their origin from extraneous parts, but the latter both 

 arise from, and are inserted into, the cartilages of the ear. The cartil- 

 ages of the ear cannot be fully exposed until the muscles have been 

 examined, but it may be premised that the conchal cartilage is the large 

 trumpet-like cartilage which mainly gives to the outer ear its form ; 

 that the annular cartilage is a short tube, or ring, which is telescoped 

 on to the external auditory process, and is itself embraced by the con- 

 stricted base of the concha ; and that the scutiform cartilage is a thin 

 plate which rides on the surface of the temporal muscle, in front of the 

 base of the concha. 



Extrinsic Muscles : — 



The Parotido-auricularis, or Deprimbns Aurbm (Plate 29). This 

 muscle has the form of a broad riband. It arises from the outer surface 

 of the parotid gland ; and, passing vertically upwards, it is inserted into 

 the outer part of the base of the concha, below the opening. 



Action. — To incline the ear downwards and outwards. 



The Cervioo - auriculares, or Eetrahbntes Aurbm. There are 

 three of these, distinguished as the cervico-auricularis (or retrahens) 

 externus, medius., and intermis. They all arise from the poll in the 

 neighbourhood of the insertion of the ligamentum nuohse, and they are 

 here superposed the one to the other. Suppose the ear to be placed 

 with the opening of the concha looking directly outwards, then the 

 externus is inserted into the middle of the inner face of the concha ; the 

 medius into the outer side of the concha, beneath the opening, and 

 under cover of the parotido-auricularis muscle ; and the internus into 

 the base of the concha, on its posterior aspect, and under cover of the 

 parotid gland. 



Action. — In moderate contraction these muscles give the opening of 

 the concha an outward direction ; and when forcibly contracted they 

 direct the opening backwards as well as outwards, and incline the ear 

 towards the poll. 



The Paribto-auricdlaris Externus, or Attolbns Maximus. This is 

 a wide, membranous muscle covering the temporalis muscle. It arises 

 from the parietal crest ; and it is inserted by its upper fibres into the 

 scutiform cartilage, and by its lower into the front of the conchal 

 cartilage. Its upper fibres are, at their origin, continuous across the 

 middle line with the opposite muscle. 



Action. — To prick the ear, that is, to erect it and give its opening a 

 forward direction. 



