EAR—EASTERLING 181 
The position of these parts is shewn in the adjoining figure. 
The basal portion of the membranous cochlea, the “ductus coch- 
learis,” communicates with the sacculus by a canal, the dorsal wall 
of which is continued into the 
tegmentum vasculosum or 
membrane of Reissner, while 
the ventral wall contains the 
basilar membrane, with its 
acoustic papilla or organ of 
Corti. The space between the 
periosteum of the bony wall of 
the cochlea and the tegmentum 
is called “scala vestibuli” ; 
that between the bone and the 
basilar membrane is the “scala 
VrerTICAL MrepIAN SECTION OF THE COCHLEA 
os or A PIGEON, magnified 30 times. (After Retzius.) 
tympani. B.g. Blood-vessels; G. Ganglia in the ramus 
The scales are part of the basilaris of the cochlear portion of the acoustic 
perilymphatic space between 17 stenrana bsilars ; Mt, Membrana tector 
the membranous and the bony P.a.b. Papilla acustica basilaris; Per. Periost of 
inner ear, and are filled with the cochlea; Sc.V. Scala vestibuli; Set. Scala 
the perilymphatic fluid. tympani; 7'.v, Tegmentum vasculosum. 
The acoustic nerve enters the membranous ear near the base of 
the cochlea, and terminates by eight macule, papille, and cristz 
acusticee in the ampulle and various other dilatations. The cells of 
these terminating nervous spots are cylindrical, and end in one or 
more extremely fine filaments or hairs; they extend into the 
endolymphatic fluid, which fills the whole membranous ear, and 
contains, especially in the sacculus, numerous small otolithic crystals 
of carbonate of lime. ‘The filamentous and hairy cells take up the 
vibrations or waves of sound which are transmitted from the 
typanum through the columella to the endolymphatic fluid, and 
convey them through the acoustic nerve to the brain. 
The whole inner ear is subject to comparatively few and unim- 
portant variations, and does not throw much light upon the 
affinities of the various groups of Birds, the differences being 
restricted chiefly to the relative size of the cochlea and the position 
and size of the semicircular canals. It cannot be doubted that the 
faculty of hearing is highly developed in Birds, not only the mere 
perception of sound, but also the power of distinguishing or under- 
standing pitch, notes and melodies, or music. 
For further information concerning the minute structure of the 
‘ear, see the monumental work of G. Retzius (Das Gehdrorgan der 
Wirbelthiere, Stockholm: 1884, ii. pp. 139-198, pls. 15-20). 
EASTERLING, according to Latham, a local name for the 
WIGEON. 
