958 TEE SENSORY APPARATUSES. 



muscles to move these, an adipose cushion to ensure liberty of movement, and 

 integuments covering the whole. 



1. Caetilages of the Concha (see p. 281). 



2. Muscles of the Exteenal Eae (see p. 281). 



3. Adipose Cushion of the Exteenal Eae. 



This cushion, which is never absent — even in the most emaciated animals- 

 envelops the base of the concha in front, inwardly, and posteriorly. It facilitates 

 the movements of that organ. 



4. Integuments of the Exteenal Eae. 

 The skin covering the concha is covered with fine close hairs. That lining 

 its interior is very thin and vascular, adheres closely to the cartilage, and is 

 furnished with long silky hairs, to prevent the entrance of dust into the ear. 



Differential Chakactebs in the Auditory Apparatus of other than Soliped Animals, 



In the various kinds of animals we study, there are no notable differences in the internal ear. 



In the middle ear, there are some modifications, either in the bones or accessory parts. Id 

 Ruminants, the auditory bones are like those of the Horse, except that the handle of the 

 malleus is more curved, and the body of the incug is longer. In the Dog, the handle of the 

 malleus is covered with small, pointed processes, and the branches of the stapes are long and 

 thick. In the Pig, the branches of the latter are slight and inflected, and the base is wide 

 and thin; in a word, the stapes of this animal bears no resemblance to a stirrup; the malleua 

 is very much inflected forward. In the last two animals, no osseous nucleus is found in the 

 tendon of the stapedian muscle. 



It is needless to say that the fenestra ovalis varies with the base of the stapes. (The 

 absence of the mastoid cells in the Sheep and Goat has been already noted.) 



The Eustachian tube exists in all the animals, but tiie guttural pouches are only found in 

 Solipeds. 



In the external ear, the conchal cartilage varies much in shape. It is thin, inclined out- 

 wards, and widely open in Ruminants. In the Pig, it differs a little, according to breed, 

 though it is always much developed, sometimes erect, but most frequently drooping. In the 

 Dog, it is sometimes short and erect, sometimes broad and pendulous. It is always short, 

 pointed, erect, and open in front, in the Cat. (In this animal a small duplicature of the 

 external margin of the concha is often seen.) In Birds, the external ear is limited to the 

 auditory canal. 



Comparison between the Auditory Apparatus in Man and that op Animals. 



There is nothing to be said regarding the internal ear. The middle ear comprises the 

 same parts as that of Mammifers other than Solipeds. Tlie handle of the malleus is straighter, 

 the incus more voluminous, and the stapes thinner, proportionately, than in animals. There 

 is no bony nucleus in the stapedian muscle. The muscle of the malleus is lodged in a distinct 

 canal belonging to the Eustachian tube. 



The external ear is composed of only two cartilages : one, forming the base of the concha, 

 represents that cartilage in animals ; the other, belonging to the auditory canal, resembles the 

 annular cartilage in the Horse. The concha is very irregular in shape, and stands at an angle 

 of from 15° to 45° from the temporal bone ; it is convex superiorly, and terminates inferiorly 

 by a small lobe. On its anterior face it presents prominences and depressions; the former are 

 four in number: the helix, a fold encircling the ear behind and above; the antihelix, a con- 

 centric prominence, almost parallel with the preceding; the tragus, a triangular, pointed 

 process, covered with hair, situated in front of the auditory canal (meatus); the antitragus, 

 opposite the tragus, behind the canal, and above the lobule. The depressions are : the concha, 

 a wide cavity, limited by tlie antihelix ; the scaphoid fossa (fossa innnminata) situated above 

 the latter; and the/o88a triangularis comprised between the helix and antihelix. 



The pavilion of the ear is traversed by several muscular fasciculi, which can have no 

 influence on its movements. The concha has also extrinsic muscles — the anterior auricu- 

 htris (attrahens aurem), auricularis superioris (attolens aurem), and the auricularis posteriores 

 (retrahens aurem). The action of these on the concha is very slight. 



