189 
THE ANATOMY OF BIRDS.—NEUROLOGY. 
stapes were‘unstepped (in life, of course, both these “ windows” are closed by membranous 
Now in birds the cochlear cavity and its bony or cartilaginous contents are only the 
beginnings of such structure— a strap-shaped or tongue-like protrusion from the vestibule, as 
if a part of the first mammalian whorl, and very incompletely divided into scala vestibuli and 
curtains). 
Fig. 84. Fia. 85. Fig. 86. Fia. 87. Fig. 88. 
Figs. 84, 85, membranous labyrinth of Haliaétus albicilla, x2. a, b, cochlea; b, its saccular extremity (or lagena); c, vestibule; 
g, its utricle; d, anterior or superior vertical semicircular canal; e, external or horizontal semicircular canal; f, posterior or inferior 
vertical semicircular canal; h, membranous canal leading into aqueduct of the vestibule; &, vascular membrane covering the scala 
vestibuli; opposite this, at i, are seen the edges of the cartilaginous prisms in the fenestra rotunda; from the edges of these cartilages 
proceeds the delicate membrane closing the opening of the cochlea (not shown in the fig.). ass 
Fig. 86, part of the superior vertical semicircular cana], showing its ampulla (which is the dilatation of the base of any semicircu- 
lar canal), nerve of ampulla, artery and connective tissue of the perilymph, x 3. a, that part of the vestibule (alveus) next to the ampulla; 
b, the dilatation of the ampulla at its vestibular opening; c, where it passes into the canal proper ; d, the canal, furnished with connec- 
tive tissue of the perilymph along its concave border and sides, as appears clearly at the sections e and f; g, nerve of the ampulla; kh, 
artery of the connective tissue, running beneath it, remote from the wall of the duct. 
Fig. 87, cochlea, x 3. a, external, b, internal, cartilaginous prism; c, membranous zone; d, saccular extremity of the cochlea, or 
lagena; e, vascular membrane; /, auditory nerve, its middle fascicle penetrating the internal cartilaginous prism, to reach the mem- 
\branous zone by its terminal filaments; g, auditory nerve, its posterior fascicle, running to the most posterior part of the lagena; h, 
filament to ampulla of posterior or inferior vertical semicircular canal. 
Fig. 88, section of the cochlea, X 3. a, vestibular surface of external cartilaginous prism, extending into d, the lagena; c, section of 
the membranous zone; e, Huschke’s process of the fenestra, which, with the margins of the cartilaginous prisms, affords attachment 
to the blind sac ,f, occluding the fenestra of the cochlea; g, spongy vascular membrane of the scala vestibuli; h, auditory lamellz of 
Treviranus; i, canals in posterior wall of the lagena, by which the nervous filaments enter its cavity. : 
(From Ibsen’s Anatomiske Underspgelser over @rets Labyrinth. 4to, Kjbenhavn, 1881, p. 17, pl. 1, figs. 13-17.) 
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ing semicircular canals ; opening into tympanum by fenestra ova- 
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it 
mouths of the separate or un 
lis ; conducting 
In the 
eagle, if its irregularities of contour were smoothed out, it would about hold a pea. 
In the language of human anatomy, the three semicircular canals are the (a) anterior or 
superior vertical, the (6) posterior or inferior vertical, and the (¢) external or horizontal; and 
the planes of their respective loops are appro 
tely mutually perpendicular, in the three 
xima' 
