BIRD. 103 BIBD. uism of this class is not in the larynx, but at the lower or pectoral end of the windpipe, in an organ called the syrinx, which consists of several stretched and vibratory membranes, tracheal rings and controlling muscles. This complicated organ, peculiar to birds, presents almost un- limited modifications, and is quite unlike the arrangement of laryngeal vocal cords in mam- mals, for the tongue has nothing to do with a bird's speech or nuisic. (See Phite, Figs. 7. 8, 14.) Further consideration of the singing of birds leads into the domain of their evolution. The Ei/€S of Birds are large, clear, highly per- fected in structure, and, in many species, en- dowed with a power of vision which' is beyond anything known elsewhere. The way in which vultures descend upon carrion from a height where they are invisible to us, or sea-birds swoop down upon fishes, or fly-catchers dart long dis- tances upon insects so small we can barely per- ceive them at close range, are examples of their sharp-sightedness, with which is combined re- markable ability in rapidly changing the focus, as must be necessary to a bird darting swiftly upon prey it must keep constantly in view. There are no movable eyelids, but in place of them a nictitating membrane is frequently drawn over the eyeball to clean and lubricate it, or shield it from a glare. The owls and other noc- turnal birds have great power of contractility not only in the pupil, but in the whole case of the eve'. See Eye. STBCCTUHE OF THE EYE. Horizontal Section: A.cb, Anterior chamber ; P.ch, Pos- terior chamber; C, Cornea; Cb, Choroid; Co, Conjunc- tiva; Cm, Crampton's muscle; i. Iris; L, Lens; P, Pecten; y.o. Optic nerve; R, Retina; Sc, Sclerotic coat, with im- bedded osseous ring. A 'Sense' of Direction. — The so-called 'sixth sense' of orientation or direction, that is, the power of instinctively knowing and maintaining a course of flight through the air independent of TOPOOBAPBY OF A BIBD. A.— General Plumage: 1, forehead (trons); 2, lore; 3. crest; 4, crown (vertex); 5, eye; C. hindheatl (occiput); 7. nape (nucha); 8. hladneck (cervix); 9. Int«r8capular region ; 10. back proper (dorsum), iucluding 11; 11, rump (uropy- glum) ; 12, lesser tail-coverts ; 13, tall ; 14, under tall-coverts (crisaum); 1.5. leg (see C) ; 16. abdomen; 17, side of body; 18. breast (pectus); 19, primaries; 20, secondaries or cubl- tals; 21, tertiaries or greater coverts; 22, coverts; 23. alula, or bastard wing; 24. throat, the lower halt of which is called 'jugulum'; 25. ear-coverts (auriculars) ; 2*!, cheek or malar region; 27, chin (mentum) ; 28, beak (see B); 29. nostril. B.— Parts of the Beak and Face: 1, culnien (ridge of upper mandible); 2. apex, tip. or hook; 3, tooth on cutting ed)^ of upper mandible; 4, Junction (gonys) of rami of lower mandible; 5, cere; 6, nostril; 7, left lore; 8. corner of mouth (commissure); 9. chin (mentum). C — Part« of the Leg: 1. Thigh (tlblotarsus; 2, tarsus (metatarsus); 3. first or hind toe (hallux); 4, second or Inner toe ; 5, third or middle toe; 6, fourth or outer toe.
