BIBD. 102 BIBD. warmth necessary to their hatching — a process which requires from two to six weeks according to size and other factors. This necessity has developed a body of instincts, habits, and mental and structural characteristics, which include the most striking, significant, and interesting facts of bird life and history. See Xidification. Nervous System. The nervous system of birds is highly developed, but presents few sali- ent difl'erences from the vertebrate type. There is a perceptible improvement of the brain over that of reptiles, more especially in the increased proportional development of the cerebral hemi- spheres; but the surface-convolutions and other features that play so important a part in the Chs.^^ Cbl.Tru Olji ' "^**'^ir*s-»^ '^'^ BBAIN OF A PIGEON. 1. Dorsal Aspect: 2. Lateral Aspect: 0. n, Olfactor.v nerves; O}. I. Olfactory love: C. hs. Cerebral hemiHphere; Cbltji. Cerebellum : P. g. Pineal gland ; Op. I. Optic lolie : ttl. Ob. Medulla oblongata ; Sp. c. Spinal cord ; P. b. Pituitary body. brains of the higher mammals are absent or merely indicated. In this, and in the way the cerebral nerves originate, the brain remains near- ly reptilian. The sympathetic system is highly developed, as would be expected in creatures of such activity and sensitiveness. See Nervous System, Evolution of. The t^enses of Birds, as a whole, equal those of most mammals, and in some directions are supe- rior to those of other animals. Taste is, perhaps, feeblest, the horny nature of the jaws and the character of the food not favoring the develop- ment of this sense in birds; yet a certain amount of discrimination is undoubtedly exercised by them, apart from the guidance of touch and smell. Odors affect birds also, but to a less degree probably than is frequent among even reptiles, not to say mammals; and it is probable that even the carrion-eating species depend little upon their sense of smell in guiding them even to odoriferous food. Birds owe less to the sense of touch than many other creatures, for they have few tactile organs, the bristles about their beaks having other purposes, mainly. The bills of some mud-hunting species, however, are spe- cialized in this direction (see Duck and Snipe). In respect to hearing, birds are well endowed, having the internal apparatus of the ear (see Eak) highly perfected, and exposed to the vi- brations of the air through a cartilaginous meatus with a fairly wide opening. One fiuiction of the ears of birds, as well as of other creatures, seems to be to inform the animal as to its re- lations with space, balance, direction, etc. Whether or not this is to be regarded as a sense, is undecided. There is no external ear, the near- est approach being in the nocturnal owls (where the organ presents other peculiarities — see Owl), though the so-called 'ears' of some of those birds are merely tufts of feathers which have nothing to do with audition. Moreover, this faculty in birds extends beyond mere quick perception of sounds to 'the power of distinguishing or under- standing' pitch, notes and melodies, or music; and it has been an important factor in the develop- ment of bird-singing. The vocal performances of birds are one of their foremost and most pleasing characteristics; yet of onl}' a few, in the most highly organized classes, can it be said that they sing. Even in the order called 'singers' (Oscines), many make little melody, though, like the crow-, they may utter a long list of significant notes — a real lan- guage, which is developed among birds generally to a degree realized bv few. The vocal mecha- anatomy 1. — Limbs as related to the general skeleton : .Sea, scap- ula; liu. humerus: cor. coracoid: r. radius: ca. carpus; di, d/. digits: r.in.t.c.p. carpometacarpus; sf, sternum; kl. keel of sternum: ui, ulna: p.y. pygostyle: fe. femur; ff. fibula; /. tibiotarsus ; f.m.f.s. tarsonu'tatarsus. 2. — Vertebra- of the tail and plowshare bone (pygost.vle). 3. — Shoulder-girdle and carinate sternum : Fu (cl). fnr- culum or 'wishbone' (clavicles): g. glenoid cavity for hu- merus: Sea. scapula; r, vert^-bral ijortion of rib; s. steriml portion of rib: vn.p.. uncinate process. Cor. coracoid; f. articulation of c()racoid with sternum ; st. sternum ; kl, keel (carina) of steriuim. 4. — Non-carinat^' Sternum (of a ratite bird) : Cg. eg. cora- coid grooves: alp. alp. lateral processes of anterior end: pe. posterior end : kl. position of keel. 5. — Side view of tile right side of the Pelvis of an adult Fowl: 11. Ilium: Is. ischium; /*6, pubis; f^A dorso-lumbar vertebne: Cd, caudal vertebne; Aw. acetabulum, with its perforated floor; P. pygost.vle. 6.— Wing of a Fowl, embryo (x) and adult (y) : li, radius; U, ulna : r. radial carpal ; u, ulnar carpal ; rd i. ', * , distal carpals : M ', = ,^,*. metacarpals; Pti, phalanges. This exhibits coales<-ence of bones with age. 7.— Viscera (of a Duck): T. trachea, ending below in syrinx (see Fig. 14) ; H, heart; v, portion of anterior wall of the botl.y cavity; ^.'o. /;//,?, coraco-furcular ligament : P. axilinry sac (lying between the coracoid, scapula and the anterior ribs, and communicating with the sub-bronchial air-sacs) ; .S. sub-clavius muscle ; /.>ir. lung: Cor, coracoid; Pa, pectoral artery ; Pv, pectoral vein: /*H/.a, pulmonar.y artery ;• point of entrance of bronchi intr» lungs; S. S. partition walls between the anterior intermediate air-sacs: SI, SI. partition walls between anterior and posterior in- tormedlate air-sacs; f, anterior intermediate* air-sacs; +t, posterior intermediate alr-sncs: F.oft.. fibrous oblique septum : P. pectoralls ma|or ; /', furcula ; .S./;^., suspensory OF BIRDS. falciform ligament; r.cL.. right coronary ligament of the liver; l.cL.. left coronary ligament of tlie liver: r.Abd.tt., right abdominal posterior air-sac; l.Abd.6.. left ditto; Oe, cpsopbagus; Aa. innominate arter.v ; and Ta. innominate vein, with their branches. 8.— -Convoluted windpipe (of an ibis) : 11'. windpipe (trachea) , Fw, furculum ; Cor. coracoid; r. 6.. right bron- chus; l.b., left bronchus; .S7. sternum. y. — Alimentar.v canal (of a Fowl):a'. oesophagus; In, crop; pr. proventriculus; gi. gizzard; d. duodenum; am, lower part of small intestine; ic. intestinal ca'ca ; r. rec- tum; cl. cloaca; J. liver; gb. gall-bladder; p. pancreas; u u. ureters; or, left oviduct (the right oviduct is rudi- inentar.v). 10. — Muscles of the wing (of a (ioose): Bi, biceps; Elast. Sec. vinculum elnsticum ; ICxp, srr. expansor secumiiorum ; Lig. ligament: Mpt. nn-lupjitagiuni : Pect, pectoral muscle ('breast'): 1'rvpt, propatagium ; I't. Ig. and Pt. hr, long and short propatagials; Tri. triceps. 11 — Musclesofthe Leg : ^/uf. 2, gluteus maximus; Olat. 4. gluteus luedins; Glut. 4, gluteus minimus; (ihit. ant, gluteus anterior; Vasts, vastus exteriius and vastus In- ternus; Obt. intent, obturator iuternus; Cnireus, cru- rens : Semitead, semltendinosus ; Feintt-Cntidl, femero- caudal; /?;Ve;*s.bireps femoris; .ttibienB. anibiens; Longs, hall, longus hallucis. 1'2— Structure of the inner Ear: Q. quadrate bone : Pter, right pterygoid; F. .1/.. foramen magnum; Cd, occipital condyle; /., lageiia ; f'o. columella auris : II. horizontal eemictrcular canal ; .S. sagittal semicircular canal. 13 — Section across the Nasal Channel of a liird's Beak. 14— Typical form ofabronchial Syrinx In I'asserlne Birds: a, front view; i^, side view, showing position of external tympanic membranes ; tr. tracheo-claviciilar muscles. 15— Plantar Tendons (Passerine type) ; ffi. flexor perfo- rans, dividing to 2d, 3d, and 4th toes; fh, flexor hallucis. .i
