588 



SCIENCE. 



[Vol. U., No. 39. 



teriial (6) cartilaginous prisms sliown in figs. 

 8 and 9. Tlie cochlea ends with a saccular 

 part, termed the ' lagena.' Details of the soft 

 parts — membranous, vascular, and nervous 

 • — will readilj-be made out from Professor 

 Ibsen's beautiful figures, here reproduced (figs. 

 5, G, 8, 9), with ample explanatory' text. 



The vestibule hardlj' requires special de- 

 scription, after examination of figs. 5 and C. 

 In the eagle, if its irregularities of contour 

 were smoothed out, it would about hold a pea. 

 Its utricular recess (</) is well developed. 



In the language of human anatomj', the 

 three semicircular canals are the anterior or 

 superior vertical, the posterior or inferior ver- 

 tical, and the external or horizontal ; and the 

 planes of their respective loops are approxi- 

 mately perpendicular to one another in the 



tal one, e, which tilts down backward. The 

 verticalit}' of the planes of d and/ is preserved. 

 The canals in birds might be better known as 

 the superior (d) and inferior (/) vertical, 

 and horizontal (e) ; though it is not probable, 

 viewing the great variation in the axes of this 

 part of the skull, that any terms descriptive 

 of direction will apply perfectly to all birds. 

 Whatever its inclination backward, there -is no 

 mistaking d, which is much the longest of the 

 three, looping high over the rest, exc"''".!. 

 the petrosal, and partly bedded in the o ' , 



with the upper limb bas-relieved upon tne inner 

 surface of the skull (fig. 4, asc). The one 

 marked / loops lowest of all, though little, if 

 any of it, reaches farther back than d; it is 

 the second in size, and quite circular (rather 

 more than a semicircle) . Its upper limb joins 



Figs. 5, 6. — Membi-auous .labyrinth of I/aliacivs aibicilla, ^ 2. a, b, cochlea; h, its saccular exti 

 g, its utricle; (?, anterior or superior vertical sernicircular canal; c, external or horizontal se 

 inferior vertical semicircular canal ; h, uiembraDous canal leading into aqueduct of the vestibule 

 X\ie &cala vestibulu Opposite |hi8, at z, are seen the edges of the cartilaginous prisms in the ,/>» 

 these cartilages proceeds the delicate membrane closing the opening of the cochlea (not si 



Fig. 7. — Part of the euperioi' vertical semicircular canal, showing its ampulla, nerve of a 

 perilymph, x 3. a, that part of the vestibule (alveus) next to the ampulla 



opening; c, where it passes into the canal propi 

 border and sides, as appears clearly at the secti( 

 beneath it, remote from the wall of the duct. 

 Fig. S. — Cochlea, x 3. «, external, 6, internal, 

 or lagena; e, vascular membrane; /, auditory n 

 membranous zone by its terminal tilaraents: 

 the lagena; A, filament to ampulla of posterior 

 Fig. 9. — Section of the cochlea, a, vestibular sur!, 

 the membranous zone; e, Huschke's process of il 

 ment to tlie blind sac, /, occluding the fenestra of 

 lamellae of Treviranus; z, canals in posterior 

 ' (From. Ibsen's Anatomiske undcrsogelser over 



a, the canal, fur 



e and /; 



rtilagin 



shed with connect! 

 ve of the ampulla 



us prism; c, membranous zone; d. i 

 ddle fascicle penetrating the internal 

 <7, auditory nerve, its posterior fascicle runni 

 ■ infirior vertical semicircular canal. 

 an- uf rxl^-rnal cartilaginous prism 

 ch, witli the margin 

 r llir c.clika; (/. spongy vascular membra 

 11 uf the lagena,by whicl'i the nervous filamc 

 els labyrinth. Kjobenhavn, 1881, p. 17, pi. 1 



emity (or lagena); c, vestibule; 



nicircular canal; /, posterior or 

 k, vascular membrane covering 



■fitra rotunda : from the edges of 

 vn in the figure). 



la. artery, and connective tissue of the 

 ation of' the ampulla at its vestibular 



rtery of the connective tissue, running 



d, saccular extremity of the cochlea^ 



cartilaginous prism, to reach the 



e running to the most posterior part of 



ti-nding into tf, the lagena; c, section of 

 the cartilaginous prisms, afi'oi'ds attacb- 

 branc of the scula vestibuli; h, auditory 

 micnts enter its cavity. 

 13-17.) 



three planes of anj- cubical figure. In birds, 

 these terms do not applj- so Well to the situa- 

 tion of the canals with reference to the axes 

 of the body, nor to the direction of their loops ; 

 neither is their mutual perpendicularity so 

 nearly exhibited. The whole set is tilted 

 over backward to some extent, so that the 

 anterior (though still superior) canal, d, in 

 figs. 5 and G, loops back bej'ond either of the 

 others ; its anterior limb is also straightened 

 out. The posterior (though still inferior) 

 canal, /, loops behind and lielow the horizon- 



the lower limb of d as in man, and the two 

 open by one orifice in the vestibule; but, as 

 far as the bonj- tubes are concerned, it is not 

 simple union, for the two limbs, before form- 

 ing a common tube, twine half around each 

 other (like two fingers of one hand crossed). 

 The loop of / reaches very near the back of 

 the skull (outside). The horizontal canal, e, 

 is the smallest, and, as it were, set within the 

 loop of/; its plane, the opposite of that of/. 

 The bony cav-ities of e and /intercommunicate 

 where they cross, at or near the point of their 



