ANATOMY OF REGIONS 
149 
This membrane has three layers: a middle one, fibrous, forming 
the membrana proper; an internal, the mucous membrane of the 
middle ear; and an external, formed only of the epidermic layer of 
the skin of the external ear. 
We must also mention the presence of an adipous cushion 
which is always present, even in the leanest animals, and which 
surrounding the base of the concha forward, inwards and back¬ 
wards, facilitates the motion of the organ. 
Blood Vessels and Nerves .—The arteries of the ear are: the 
anterior auricular, coming from the temporal trunk, and which 
carries the blood to the internal face of the concha; the posterior 
auricular, furnished by the external carotid which runs between 
the skin and the cartilage—one of the divisions of which goes to 
the middle ear, and another to the adipous cushion. 
The veins of the same name are larger than the arteries. They 
often anastomose together. The anterior auricular vein is almost 
always double. 
The nerves are furnished by the second cervical pair and by 
the middle auricular, a branch of the facial. The former goes to 
the external tegument. The branches of the second going to the 
ear, are distributed to the internal face of the concha. 
The diverse motions of the ear are produced by the muscles 
already described in the temporal and parotid regions. 
The parotido auricularis carries the ear down and outwards; 
the zygomatico auricularis, external temporo auricularis, and ex~ 
ternal scuto auricularis, carry the opening of the concha forward ; 
the internal temporo auricularis is antagonist to the parotido au¬ 
ricularis, therefore an adductor of the ear; the internal scuto 
auricularis turns the opening of the cartilaginous concha outwards. 
Of the three cervico auricularis, the superficial pulls the ear back¬ 
wards and downwards, so do the middle and superior, but their 
insertion outwards on the concha, allow them to turn the opening 
of the cartilage outwards, and even backwards, according to the 
extent of their contraction. 
Differences .—The size of the ear of the donkey and of the 
mide are proverbial; it is much longer than that of the horse, 
and is necessarily more inclined outwards. The thickness and 
