[1] Lord Breadalbane (d. 1871) was perhaps the first large landowner
who set the example that has been since followed by others. On his
unrivalled forest of Black Mount, eagles--elsewhere persecuted to the
death--were by him ordered to be unmolested so long as they were not
numerous enough to cause considerable depredations on the farmers'
flocks. He thought that the spectacle of a soaring eagle was a
fitting adjunct to the grandeur of his Argyllshire mountain scenery,
and a good equivalent for the occasional loss of a lamb, or the
slight deduction from the rent paid by his tenantry in consequence.
[2] As already stated, the site chosen varies greatly. Occasionally
placed in a niche in what passes for a perpendicular cliff to which
access could only be gained by a skilful cragsman with a rope, the
writer has known a nest to within 10 or 15 yds. of which he rode on a
pony. Two beautiful views of as many golden eagles' nests, drawn on
the spot by Joseph Wolf, are given in the _Ootheca Wolleyana_, and a
fine series of eggs is also figured in the same work.
[3] Which species may have been the traditional emblem of Roman
power, and the _Ales Jovis_, is very uncertain.
EAGLEHAWK, a borough of Bendigo county, Victoria, Australia, 105 m. by
rail N.N.W. of Melbourne and 4 m. from Bendigo, with which it is
connected by steam tramway. Pop. (1901) 8130. It stands on the Bendigo
gold-bearing reef, and its mines are important.
EAGRE (a word of obscure origin; the earliest form seems to be _higre_,
Latinized as _higra_, which William of Malmesbury gives as the name of
the bore in the Severn; the _New English Dictionary_ rejects the usual
derivations from the O. Eng. _eagor_ or _egor_, which is seen in
compounds meaning "flood," and also the connexion with the Norse sea-god
_Aegir_), a tide wave of great height rushing up an estuary (see BORE),
used locally of the Humber and Trent.
EAKINS, THOMAS (1844- ), American portrait and figure painter, was
born at Philadelphia, on the 25th of July 1844. A pupil of J.L. Gerome,
in the Ecole des Beaux-Arts, Paris, and Also of Leon Bonnat, besides
working in the studio of the sculptor Dumont, he became a prolific
portrait painter. He also painted genre pictures, sending to the
Centennial Exhibition at Philadelphia, in 1876, the "Chess Players," now
in the Metropolitan Museum of Art, New York. A large canvas, "The
Surgical Clinic of Professor Gross," owned by Jefferson Medical College,
Philadelphia, contains many life-sized figures. Eakins, with his pupil
Samuel Murray (b. 1870), modelled the heroic "Prophets" for the
Witherspoon Building, Philadelphia, and his work in painting has a
decided sculptural quality. He was for some years professor of anatomy
at the schools of the Pennsylvania Academy of Fine Arts in Philadelphia.
A man of great inventiveness, he experimented in many directions,
depicting on canvas modern athletic sports, the negro, and early
American life, but he is best known by his portraits. He received awards
at the Columbian (1893), Paris (1900), Pan-American (1900), and the St
Louis (1904), Expositions; and won the Temple medal in the Pennsylvania
Academy of Fine Arts, and the Proctor prize of the National Academy of
Design.
EALING, a municipal borough in the Ealing parliamentary division of
Middlesex, England, suburban to London, 9 m. W. of St Paul's cathedral.
Pop. (1891) 23,979; (1901) 33,031. The nucleus of the town, the ancient
village, lies south of the highroad to Uxbridge, west of the open Ealing
Common. The place is wholly residential. At St Mary's church, almost
wholly rebuilt c. 1870, are buried John Oldmixon, the historian (d.
1742), and Horne Tooke (d. 1812). The church of All Saints (1905)
commemorates Spencer Perceval, prime minister, who was assassinated in
the House of Commons in 1812. It was erected under the will of his
daughter Frederica, a resident of Ealing. Gunnersbury Park, south of
Ealing Common, is a handsome Italian mansion. Among former owners of the
property was Princess Amelia, daughter of George II., who lived here
from 1761 till her death in 1786. The name of Gunnersbury is said to be
traceable to the residence here of Gunilda, niece of King Canute. The
manor of Ealing early belonged to the see of London, but it is not
mentioned in Domesday and its history is obscure.
EAR (common Teut.; O.E. _eare_, Ger. _Ohr_, Du. _oor_, akin to Lat.
_auris_, Gr. [Greek: ous]), in anatomy, the organ of hearing. The human
ear is divided into three parts--external, middle and internal. The
external ear consists of the pinna and the external auditory meatus. The
pinna is composed of a yellow fibro-cartilaginous framework covered by
skin, and has an external and an internal or cranial surface. Round the
margin of the external surface in its upper three quarters is a rim
called the helix (fig. 1, a), in which is often seen a little prominence
known as Darwin's tubercle, representing the folded-over apex of a
prick-eared ancestor. Concentric with the helix and nearer the meatus is
the antihelix (c), which, above, divides into two limbs to enclose the
triangular fossa of the antihelix. Between the helix and the antihelix
is the fossa of the helix. In front of the antihelix is the deep fossa
known as the concha (fig. 1, d), and from the anterior part of this the
meatus passes inward into the skull. Overlapping the meatus from in
front is a flap called the tragus, and below and behind this is another
smaller flap, the antitragus. The lower part of the pinna is the lobule
(e), which contains no cartilage. On the cranial surface of the pinna
elevations correspond to the concha and to the fossae of the helix and
antihelix. The pinna can be slightly moved by the anterior, superior and
posterior auricular muscles, and in addition to these there are four
small intrinsic muscles on the external surface, known as the helicis
major and minor, the tragicus and the antitragicus, and two on the
internal surface called the obliquus and transversus. The external
auditory meatus (fig. 1, n) is a tube running at first forward and
upward, then a little backward and then forward and slightly downward;
of course all the time it is also running inward until the tympanic
membrane is reached. The tube is about an inch long, its outer third
being cartilaginous and its inner two-thirds bony. It is lined by skin
in its whole length, the sweat glands of which are modified to secrete
the wax or cerumen.
[Illustration: FIG. 1.--The Ear as seen in Section.
a, Helix. m, Tip of petrous process.
b, Antitragus. n, External auditory meatus.
c, Antihelix. o, Membrana tympani.
d, Concha. p, Tympanum.
e, Lobule. 1, points to malleus.
f, Mastoid process. 2, to incus.
g, Portio dura. 3, to stapes.
h, Styloid process. 4, to cochlea.
k, Internal carotid artery. 5, 6, 7, the three semicircular canals.
l, Eustachian tube. 8 and 9, facial and auditory nerves.]
The middle ear or tympanum (fig. 1, p) is a small cavity in the temporal
bone, the shape of which may perhaps be realized by imagining a hock
bottle subjected to lateral pressure in such a way that its circular
section becomes triangular, the base of the triangle being above. The
neck of the bottle, also laterally compressed, will represent the
Eustachian tube (fig. 1, l), which runs forward, inward and downward, to
open into the naso-pharynx, and so admits air into the tympanum. The
bottom of the bottle will represent the posterior wall of the tympanum,
from the upper part of which an opening leads backward into the mastoid
antrum and so into the air-cells of the mastoid process. Lower down is a
little pyramid which transmits the stapedius muscle, and at the base of
this is a small opening known as the iter chordae posterius, for the
chorda tympani to come through from the facial nerve. The roof is formed
by a very thin plate of bone, called the tegmen tympani, which separates
the cavity from the middle fossa of the skull. Below the roof the upper
part of the tympanum is somewhat constricted off from the rest, and to
this part the term "attic" is often applied. The floor is a mere groove
formed by the meeting of the external and internal walls. The outer wall
is largely occupied by the tympanic membrane (fig. 1, o), which entirely
separates the middle ear from the external auditory meatus; it is
circular, and so placed that it slopes from above, downward and inward,
and from behind, forward and inward. Externally it is lined by skin,
internally by mucous membrane, while between the two is a firm fibrous
membrane, convex inward about its centre to form the umbo. Just in front
of the membrane on the outer wall is the Glaserian fissure leading to
the glenoid cavity, and close to this is the canal of Huguier for the
chorda tympani nerve. The inner wall shows a promontory caused by the
cochlea and grooved by the tympanic plexus of nerves; above and behind
it is the fenestra ovalis, while below and behind the fenestra rotunda
is seen, closed by a membrane. Curving round, above and behind the
promontory and fenestrae, is a ridge caused by the aqueductus Fallopii
or canal for the facial nerve. The whole tympanum is about half an inch
from before backward, and half an inch high, and is spanned from side to
side by three small bones, of which the malleus (fig. 1, 1) is the most
external. This is attached by its handle to the umbo of the tympanic
membrane, while its head lies in the attic and articulates posteriorly
with the upper part of the next bone or incus (fig. 1, 2). The long
process of the incus runs downward and ends in a little knob called the
os orbiculare, which is jointed on to the stapes or stirrup bone (fig.
1, 3). The two branches of the stapes are anterior and posterior, while
the footplate fits into the fenestra ovalis and is bound to it by a
membrane. It will thus be seen that the stapes lies nearly at right
angles to the long process of the incus. From the front of the malleus a
slender process projects forward into the Glaserian fissure, while from
the back of the incus the posterior process is directed backward and is
attached to the posterior wall of the tympanum. These two processes form
a fulcrum by which the lever action of the malleus and incus is brought
about, so that when the handle of the malleus is pushed in by the
membrane the head moves out; the top of the incus, attached to it, also
moves out, and the os orbiculare moves in, and so the stapes is pressed
into the fenestra ovalis. The stapedius and tensor tympanic muscles, the
latter of which enters the tympanum in a canal just above the
Eustachian tube to be attached to the malleus, modify the movements of
the ossicles.
The mucous membrane lining the tympanum is continuous through the
Eustachian tube with that of the naso-pharynx, and is reflected on to
the ossicles, muscles and chorda tympani nerve. It is ciliated except
where it covers the membrana tympani, ossicles and promontory; here it
is stratified.
[Illustration: FIG. 2.--Diagram of the Membranous Labyrinth.
DC, Ductus cochlearis.
dr, Ductus reuniens.
S, Sacculus.
U, Utriculus.
dv, Ductus endolymphaticus.
SC, Semicircular canals.
(After Waldeyer.)]
The internal ear or labyrinth consists of a bony and a membranous part,
the latter of which is contained in the former. The bony labyrinth is
composed of the vestibule, the semicircular canals and the cochlea. The
vestibule lies just internal to the posterior part of the tympanum, and
there would be a communication between the two, through the fenestra
ovalis, were it not that the footplate of the stapes blocks the way. The
inner wall of the vestibule is separated from the bottom of the internal
auditory meatus by a plate of bone pierced by many foramina for branches
of the auditory nerve (fig. 1, 9), while at the lower part is the
opening of the aqueductus vestibuli, by means of which a communication
is established with the posterior cranial fossa. Posteriorly the three
semicircular canals open into the vestibule; of these the external (fig.
1, 7) has two independent openings, but the superior and posterior (fig.
1, 5 and 6) join together at one end and so have a common opening, while
at their other ends they open separately. The three canals have
therefore five openings into the vestibule instead of six. One end of
each canal is dilated to form its ampulla. The superior semicircular
canal is vertical, and the two pillars of its arch are nearly external
and internal; the external canal is horizontal, its two pillars being
anterior and posterior, while the convexity of the arch of the posterior
canal is backward and its two pillars are superior and inferior.
Anteriorly the vestibule leads into the cochlea (fig. 1, 4), which is
twisted two and a half times round a central pillar called the modiolus,
the whole cochlea forming a rounded cone something like the shell of a
snail though it is only about 5 mm. from base to apex. Projecting from
the modiolus is a horizontal plate which runs round it from base to apex
like a spiral staircase; this is known as the lamina spiralis, and it
stretches nearly half-way across the canal of the cochlea. At the summit
it ends in a little hook named the hamulus. The modiolus is pierced by
canals which transmit branches of the auditory nerve to the lamina
spiralis.
[Illustration: FIG. 3.--cl, Columnar cells covering the crista acustica;
p, peripheral, and c, central processes of auditory cells; n, nerve
fibres. (After Ruedinger.)]
The membranous labyrinth lies in the bony labyrinth, but does not fill
it; between the two is the fluid called perilymph, while inside the
membranous labyrinth is the endolymph. In the bony vestibule lie two
membranous bags, the saccule (fig. 2, S) in front, and the utricle (fig.
2, U) behind; each of these has a special patch or macula to which twigs
of the auditory nerve are supplied, and in the mucous membrane of which
specialized hair cells are found (fig. 3, p).
Attached to the maculae are crystals of carbonate of lime called
otoconia. The membranous semicircular canals are very much smaller in
section than the bony; in the ampulla of each is a ridge, the crista
acustica, which is covered by a mucous membrane containing sensory hair
cells like those in the maculae. All the canals open into the utricle.
From the lower part of the saccule a small canal called the ductus
endolymphaticus (fig. 2, dv) runs into the aqueductus vestibuli; it is
soon joined by a small duct from the utricle, and ends, close to the
dura mater of the posterior fossa of the cranium, as the saccus
endolymphaticus, which may have minute perforations through which the
endolymph can pass. Anteriorly the saccule communicates with the
membranous cochlea or scala media by a short ductus reuniens (fig. 2,
dr). A section through each turn of the cochlea shows the bony lamina
spiralis, already noticed, which is continued right across the canal by
the basilar membrane (fig. 4, bm), thus cutting the canal into an upper
and lower half and connected with the outer wall by the strong spiral
ligament (fig. 4, sl). Near the free end of the lamina spiralis another
membrane called the membrane of Reissner (fig. 4, mR) is attached, and
runs outward and upward to the outer wall, taking a triangular slice out
of the upper half of the section. There are now three canals seen in
section, the upper of which is the scala vestibuli (fig. 4, SV), the
middle and outer the scala media, ductus cochlearis or true membranous
cochlea (fig. 4, DC), while the lower is the scala tympani (fig. 4, ST).
The scala vestibuli and scala tympani communicate at the apex of the
cochlea by an opening known as the helicotrema, so that the perilymph
can here pass from one canal to the other. At the base of the cochlea
the perilymph in the scala vestibuli is continuous with that in the
vestibule, but that in the scala tympani bathes the inner surface of the
membrane stretched across the fenestra rotunda, and also communicates
with the subarachnoid space through the aqueductus cochleae, which opens
into the posterior cranial fossa. The scala media containing endolymph
communicates, as has been shown, with the saccule through the canalis
reuniens, while, at the apex of the cochlea, it ends in a blind
extremity of considerable morphological interest called the lagena.
[Illustration: FIG. 4.--Transverse Section through the Tube of the
Cochlea.
m, Modiolus. bm, Basilar membrane.
0, Outer wall of cochlea. cs, Crista spiralis.
SV, Scala vestibuli. sl, Spiral ligament.
ST, Scala tympani. sg, Spiral ganglion of auditory nerve.
DC, Ductus cochlearis. oc, Organ of Corti.
mR, Membrane of Reissner.]
The scala media contains the essential organ of hearing or organ of
Corti (fig. 4, oc), which lies upon the inner part of the basilar
membrane; it consists of a tunnel bounded on each side of the inner and
outer rods of Corti; on each side of these are the inner and outer hair
cells, between the latter of which are found the supporting cells of
Deiters. Most externally are the large cells of Hensen. A delicate
membrane called the lamina reticularis covers the top of all these, and
is pierced by the hairs of the hair cells, while above this is the loose
membrana tectoria attached to the periosteum of the lamina spiralis,
near its tip, internally, and possibly to some of Deiter's cells
externally. The cochlear branch of the auditory nerve enters the lamina
spiralis, where a spiral ganglion (fig. 4, sg) is developed on it; after
this it is distributed to the inner and outer hair cells.
[Illustration: FIG. 5.--Transverse Section of Corti's Organ from the
Central Coil of Cochlea (Retzius).
(From R. Howden--Cunningham's _Text-Book of Anatomy_.)]
For further details see _Text-Book of Anatomy_, edited by D.J.
Cunningham (Edinburgh, 1906); Quain's _Elements of Anatomy_ (London,
1893); Gray's _Anatomy_ (London, 1905); _A Treatise on Anatomy_,
edited by H. Morris (London, 1902); _A Text-Book of Human Anatomy_, by
A. Macalister (London, 1889).
_Embryology._--The pinna is formed from six tubercles which appear round
the dorsal end of the hyomandibular cleft or, more strictly speaking,
pouch. Those for the tragus and anterior part of the helix belong to the
first or mandibular arch, while those for the antitragus, antihelix and
lobule come from the second or hyoid arch. The tubercle for the helix is
dorsal to the end of the cleft where the two arches join. The external
auditory meatus, tympanum and Eustachian tube are remains of the
hyomandibular cleft, the membrana tympani being a remnant of the cleft
membrane and therefore lined by ectoderm outside and entoderm inside.
The origin of the ossicles is very doubtful. H. Gadow's view, which is
one of the latest, is that all three are derived from the hyomandibular
plate which connects the dorsal ends of the hyoid and mandibular bars
(_Anatomischer Anzeiger_, Bd. xix., 1901, p. 396). Other papers which
should be consulted are those of E. Gaupp, _Anatom. Hefte, Ergebnisse_,
Bd. 8, 1898, p. 991, and J.A. Hammar, _Archiv f. mikr. Anat._ lix.,
1902. These papers will give a clue to the immense literature of the
subject. The internal ear first appears as a pit from the cephalic
ectoderm, the mouth of which in Man and other mammals closes up, so that
a pear-shaped cavity is left. The stalk of the pear which is nearest the
point of invagination is called the recessus labyrinthi, and this, after
losing its connexion with the surface of the embryo, grows backward
toward the posterior cranial fossa and becomes the ductus
endolymphaticus. The lower part of the vesicle grows forward and becomes
the cochlea, while from the upper part three hollow circular plates grow
out, the central parts of which disappear, leaving the margin as the
semicircular canals. Subsequently constrictions appear in the vesicle
marking off the saccule and utricle. From the surrounding mesoderm the
petrous bone is formed by a process of chondrification and ossification.
See W. His, Junr., _Archiv f. Anat. und Phys._, 1889, supplement, p.
1; also Streeter, _Am. Journ. of Anat._ vi., 1907.
_Comparative Anatomy._--The ectodermal inpushing of the internal ear has
probably a common origin with the organs of the lateral line of fish. In
the lower forms the ductus endolymphaticus retains its communication
with the exterior on the dorsum of the head, and in some Elasmobranchs
the opening is wide enough to allow the passage of particles of sand
into the saccule. It is probable that this duct is the same which,
taking a different direction and losing its communication with the skin,
abuts on the posterior cranial fossa of higher forms (see Rudolf Krause,
"Die Entwickelung des Aq. vestibuli seu d. Endelymphaticus," _Anat.
Anzeiger_, Bd. xix., 1901, p. 49). In certain Teleostean fishes the swim
bladder forms a secondary communication with the internal ear by means
of special ossicles (see G. Ridewood, _Journ. Anat. & Phys._ vol.
xxvi.). Among the Cyclostomata the external semicircular canals are
wanting; Petromyzon has the superior and posterior only, while in Myxine
these two appear to be fused so that only one is seen. In higher types
the three canals are constant. Concretions of carbonate of lime are
present in the internal ears of almost all vertebrates; when these are
very small they are called otoconia, but when, as in most of the
teleostean fishes, they form huge concretions, they are spoken of as
otoliths. One shark, Squatina, has sand instead of otoconia (C. Stewart,
_Journ. Linn. Society_, xxix. 409). The utricle, saccule, semicircular
canals, ductus endolymphaticus and a short lagena are the only parts of
the ear present in fish.
The Amphibia have an important sensory area at the base of the lagena
known as the macula acustica basilaris, which is probably the first
rudiment of a true cochlea. The ductus endolymphaticus has lost its
communication with the skin, but it is frequently prolonged into the
skull and along the spinal canal, from which it protrudes, through the
intervertebral foramina, bulging into the coelom. This is the case in
the common frog (A. Coggi, _Anat. Anz._ 5. Jahrg., 1890, p. 177). In
this class the tympanum and Eustachian tube are first developed; the
membrana tympani lies flush with the skin of the side of the head, and
the sound-waves are transmitted from it to the internal ear by a single
bony rod--the columella.
In the Reptilia the internal ear passes through a great range of
development. In the Chelonia and Ophidia the cochlea is as rudimentary
as in the Amphibia, but in the higher forms (Crocodilia) there is a
lengthened and slightly twisted cochlea, at the end of which the lagena
forms a minute terminal appendage. At the same time indications of the
scalae tympani and vestibuli appear. As in the Amphibia the ductus
endolymphaticus sometimes extends into the cranial cavity and on into
other parts of the body. Snakes have no tympanic membrane. In the birds
the cochlea resembles that of the crocodiles, but the posterior
semicircular canal is above the superior where they join one another. In
certain lizards and birds (owls) a small fold of skin represents the
first appearance of an external ear. In the monotremes the internal ear
is reptilian in its arrangement, but above them the mammals always have
a spirally twisted cochlea, the number of turns varying from one and a
half in the Cetacea to nearly five in the rodent _Coelogenys_. The
lagena is reduced to a mere vestige. The organ of Corti is peculiar to
mammals, and the single columella of the middle ear is replaced by the
three ossicles already described in Man (see Alban Doran, "Morphology of
the Mammalian Ossicula auditus," _Proc. Linn. Soc._, 1876-1877, xiii.
185; also _Trans. Linn. Soc._ 2nd Ser. Zool. i. 371). In some mammals,
especially Carnivora, the middle ear is enlarged to form the tympanic
bulla, but the mastoid cells are peculiar to Man.
For further details see G. Retzius, _Das Gehoerorgan der Wirbelthiere_
(Stockholm, 1881-1884); Catalogue of the Museum of the R. College of
Surgeons--Physiological Series, vol. iii. (London, 1906); R.
Wiedersheim's _Vergleichende Anatomie der Wirbeltiere_ (Jena, 1902).
(F. G. P.)