EAR EAR-RING. 



769 



stituting New Zealand, extending from lat. 34 30' 

 to 41 30' S. Its form is irregular. From lat. 37 

 SO* to 30 40' S., the breadth is from 150 to 180 

 miles ; afterwards it decreases gradually to thirty 

 miles, the distance from cape Tierawitte to cape 

 Palliser, its most southern point. 



EAR (auris). The ear is the organ of hearing. 

 It is situated at the side of the head, and is divided 

 into external and internal ear. The auricula, or 

 pinna, commonly called the ear, constitutes the ex- 

 ternal part. It is of a greater or lesser size, accord- 

 ing to the individual. The pinna is formed of a 

 fibrous cartilage, elastic and pliant : the skin which 

 covers it is thin and dry. There are also seen, upon 

 the different projections of the cartilaginous ear, 

 certain muscular fibres, to which the name of muscles 

 has been given. The pinna, receiving many vessels 

 and nerves, is very sensible, and easily becomes red. 

 It is fixed to the head by the cellular tissue, and by 

 muscles, which are called, according to their position, 

 anterior, superior and posterior. These muscles are 

 much developed in many animals : in man, they 

 may be considered as simple vestiges. The meatus 

 auditorius, or auditory passage, extends from the 

 concha to the membrane of the tympanum ; its 

 length, variable according to age, is from ten to 

 twelve lines in the adult ; it is narrower in the middle 

 than at the ends ; it presents a slight curve above 

 and in front. Its external orifice is commonly 

 covered with liairs, like the entrance to the other 

 cavities. The middle ear comprehends the cavity 

 of the tympanum, the little bones which are contained 

 in this cavity, the mastoid cells, the Eustachian tube, 

 &c. The tympanum is a cavity which separates the 

 external from the internal^ear. Its form is that of a 

 portion of a cylinder, but a little irregular. The 

 external side presents the membrana tympani. This 

 membrane is directed obliquely downward and 

 inward ; it is bent, very slender and transparent, 

 covered on the outside by a continuation of the skin ; 

 on the inside, by the narrow membrane which covers 

 the tympanum. Its tissue is dry, brittle, and has 

 nothing analogous in the animal economy ; there are 

 neither fibres, vessels, nor nerves found in it. The 

 cavity of the tympanum, and all the canals which end 

 there, are covered with a very slender mucous mem- 

 brane : this cavity, which is always full of ah-, con- 

 tains, besides, four small bones (the malleus, incus, 

 os orbiculare, and stapes), which form a chain from 

 the membrana tympani to the fenestra ovalis, where 

 the base of the stapes is fixed. There are some little 

 muscles for the purpose of moving this osseous chain, 

 of stretching and slackening the membranes to which 

 it is attached : thus the internal muscle of the malleus 

 draws it forward, bends the chain in this direction, 

 and stretches the membranes ; the anterior muscle 

 produces the contrary effect : it is also supposed that 

 the small muscle which is placed in the pyramid, and 

 which is attached to the neck of the stapes, may give 

 a slight tension to the chain, in drawing it towards 

 itself. The internal ear, or labyrinth, is composed 

 of the cochlea, of the semicircular canals, and of the 

 vestibule. The cochlea is a bony cavity, in form of 

 a spiral, from which it has taken its name. This 

 cavity is divided into two others, which are distin- 

 guished into external and internal. The partition 

 which separates them is a plate set edgeways, and 

 which, in its whole length, is partly bony and partly 

 membranous. The semicircular canals are three 

 cylindrical cavities, bent in a semicircular form, two 

 of which are disposed horizontally, and the others 

 vertically. These canals terminate by their extremi- 

 ties in the vestibule. They contain bodies of a gray 

 colour, the extremities of which are terminated by 

 swellings. The vestibule is the central cavity, the 



point of union of all the others. It communicates 

 with the tympanum, the cochlea, the semicircular 

 canals, and the internal meatus auditorius, by a great 

 number of little openings. The cavities of the in- 

 ternal ear are entirely hollowed out of the hardest 

 part of the temporal lx>ne : they are covered with an 

 extremely thin membrane, and are full of a very thin 

 and limpid fluid : they contain, besides, the acoustic 

 nerve. The internal ear and middle ear are tra- 

 versed by several nervous threads, the presence of 

 which is, perhaps, useful to hearing. 



A, helix ; B, antihelix ; C, fossa nnvicularis of 

 the antihelix ; D, groove between the helix and anti- 

 helix ; E, tragus ; F, antitragus ; G, lobe ; H, concha ; 

 I, cartilaginous portion of the auditory canal ; J, os- 

 seous portion of the auditory canal; K, internal 

 extremity of the auditory canal, closed by L,tho 

 membrana tympani, the internal or convex surface of 

 which is here seen, the walls of the tympanum 

 being removed; M, head of the malleus; N, han- 

 dle of the malleus, between the camina of the mem- 

 brana tympani ; O, processus gracilis of the malleus ; 

 P, body of the incus; Q, short crus of the incus; 

 R, long crus of the incus, articulating with S, the 

 os orbiculare ; T, stapes, its base applied against the 

 fenestra ovalis ; U, vestibule of the labyrinth ; V, 

 anterior semicircular canal ; W, posterior semicircu- 

 lar canal ; X, external semicircular canal ; Y, begin- 

 ning of the cochlea ; Z, end of the cochlea ; * aque- 

 duct of Fallopius. See Acoustics and Music. 



EAR-RING, an ornament for 

 the ear, consisting of a ring or 

 hook passing through the lobe, 

 with a pendant of diamonds, 

 pearls, or other jewels, frequently 

 attached. It seems to be in re- 

 pute among all nations, the most 

 savage as well as the most civi- 

 lized. The Roman ladies used 

 ear-rings of great value. The an- 

 nexed cut represents a gold ear- 

 ring with pearl pendants, foiuid 

 at Pompei. It is drawn the size 

 of the original. 



3c 



