872 THE SENSE ORGANS AND SKIN OF THE HORSE 
herent to the cartilage and is relatively dark in color. There are three or four 
cutaneous ridges which run about parallel with the borders of the conchal cartilage, 
but do not extend to the apex or the cavum conchw. The upper and marginal 
parts and the ridges are covered with long hairs, but the skin between the ridges 
and below is thin, covered sparsely with very fine hairs, and supplied with numerous 
sebaceous glands. In the external acoustic meatus the skin becomes thinner; in 
the cartilaginous part it is suppled with numerous large, coiled, ceruminous glands 
(Glandulz ceruminosie), and is sparsely covered with very fine hairs; in the osseous 
part the glands are small and few or absent and there are no hairs. 
THE AURICULAR MUSCLES 
The auricular muscles may be subdivided into two sets, viz., (a) extrinsic 
muscles, which arise on the head and adjacent part of the neck, and move the ex- 
ternal ear as a whole, and (b) intrinsic muscles, which are confined to the auricula. 
In this connection the scutiform cartilage may be regarded as a sesamoid cartilage 
intercalated in the course of some of the muscles. 
The extrinsic muscles are as follows: 
1. The scutularis is a thin muscular sheet situated subcutaneously over the 
temporalis muscle. Its fibers arise from the zygomatic arch and the frontal and 
parietal crests, and converge to the scutiform cartilage. It consists of three parts: 
(a) The fronto-scutularis comprises temporal and frontal parts, which arise 
from the zygomatic arch and the frontal crest, and are inserted into the lateral and 
anterior borders of the scutiform cartilage respectively. 
(b) The interscutularis arises from the parietal crest, over which it is in part 
continuous with the muscle of the opposite side. Its fibers converge to the medial 
border of the scutiform cartilage. 
(c) The cervico-scutularis is not well defined from the preceding muscle. It 
arises from the nuchal crest and is inserted into the medial border of the scutiform 
cartilage. 
2. The anterior auricular muscles (Mm. auriculares orales) are four in number: 
(a) The zygomatico-auricularis arises from the zygomatic arch and the parotid 
fascia, and is inserted into the outer face of the base of the conchal cartilage partly 
under, partly above, the insertion of the parotido-auricularis. 
(Lb) The scutulo-auricularis superficialis inferior arises on the lateral part of 
the superficial face of the scutiform cartilage and ends on the base of the conchal 
cartilage with the preceding muscle. 
(c) The scutulo-auricularis superficialis medius arises from the posterior part 
of the deep surface of the scutiform cartilage and is inserted into the dorsum of the 
conchal cartilage, close to the lower part of its anterior border, and above and behind 
the preceding muscle. It receives a slip from the cervico-scutularis. 
(d) The scutulo-auricularis superficialis superior is a thin slip which is de- 
tached from the interscutularis over the medial border of the scutiform cartilage. 
It ends on the anterior aspect of the lower part of the dorsum of the conchal car- 
tilage. 
3. The dorsal auricular muscles (Mm. auriculares dorsales) are two in 
number. 
(a) The scutulo-auricularis superficialis accessorius is a narrow band which is 
largely covered by the preceding muscle. It arises from the posterior prolongation 
and the adjacent part of the superficial face of the scutiform cartilage, and is 
inserted into the convex surface of the conchal cartilage medial to the preceding 
muscle, the two crossing each other at an acute angle. 
(b) The parieto-auricularis is flat and triangular; it arises from the parietal 
crest under cover of the cervico-scutularis, runs outward and a little backward, 
