The Ear

The external ear is inclined outward. The middle part is much wider and less curved than in the horse. The apex is also wide and does not curve forward. The lower part of the anterior border is bent backward and bears long hairs. The posterior border is thin and is regularly convex, except below, where it is indented. The opening is wide and the concave surface presents four ridges; the convex surface presents corresponding depressions. The styloid process of the conchal cartilage is short and blunt. The edges of the annular cartilage are in contact at the inner side and the upper border is notched externally. The scutiform cartilage is a very irregular quadrilateral plate; it is situated on the lateral aspect of the cranium with its concave surface in contact with the fat and temporalis muscle. The osseous external auditory meatus is directed practically straight inward; it is about twice as long as that of the horse, and tapers very gradually from without inward. The chief special characters of the auricular muscles are as follows: (1) The scutularis blends with the frontalis muscle. The interscutularis arises from the base of the processus cornu (or the corresponding area in polled cattle) and from the frontal crest. (2) The cervico-scutularis arises from the posterior surface of the cranium below the frontal eminence, and receives slips from the parieto-auricularis and cervico-auricularis superficialis. (3) The zygomatico-auricularis and scutulo-auricularis superficialis inferior are fused. (4) The scutulo-auricularis superficialis superior is distinct from the interscutularis; it arises from the superficial face of the scutiform cartilage. (5) The cervico-auricularis superficialis arises from the ligamentum nuchæ and ends on the convex surface of the conchal cartilage. (6) The parieto-auricularis arises from the nuchal surface of the frontal bone, the adjacent part of the parietal bone, and the ligamentum nuchæ; it is inserted below the preceding muscle. (7) The scutulo-auricularis superficialis accessorius arises from the superficial face of the scutiform cartilage and is inserted by a round tendon into the anterior part of the convex surface of the conchal cartilage. (8) The cervico-auricularis profundus minor consists of two fasciculi; the inner, narrow part is deep red in color, and arises from the fascia of the cervical muscles external to the occipital attachment of the ligamentum nuchæ; the outer, wider part is pale, and arises beneath the cervico-auricularis superficialis, indirectly from the scutiform cartilage. The two unite and are inserted into the lower aspect of the base of the conchal cartilage. (9) The scutulo-auricularis profundus minor arises from the temporal crest above the external auditory meatus and is inserted into the anterior part of the deep face of the scutiform cartilage.

The cavum tympani is small; it communicates ventrally with the air-cells of the bulla ossea. The tympanic membrane is nearly circular and is not so oblique as in the horse. The auditory ossicles are smaller than those of the horse; the malleus is more curved, the body of the incus is longer, and there is a small prominence on the front of the head of the stapes for the attachment of the stapedius muscle.

The Eustachian tube is small and is only about two inches long. The pharyngeal opening is small and is situated on the side of the fornix of the pharynx close to the base of the cranium. There is no flap-like expansion of the cartilage, but the inner border of the orifice is formed by a fold of mucous membrane.

The internal ear has essentially the same arrangement as in the horse.