I.

IDENTIFICA´TION, _n._ Act or process of determining to what species a specimen or a name belongs; the determination so made.

IDEN´TIFY. To determine the name of a specimen or of a species; to ascertain the identity of a certain specimen with a name, or name with a certain species.

IGNO´BLE, _a._ Said of hawks lacking the special qualities of those used in falconry.

IL´EUM, _n._ Lower portion of small intestine.

IL´IAC, _a._ Relating to the ilium, or haunch-bone; also, to the ileum.

IL´IUM, _n._ Haunch-bone; principal bone of the pelvis, forming with the ischium and pubis the _os innominatum_.

IM´BRICATED, _a._ Fixed shingle-wise with overlapping edge or end.

IMMAC´ULATE, _a._ Unspotted; not marked with different colors.

IMMATURE´, _a._ Not having yet assumed final size, shape, color, or other conditions of the adult.

IMPER´FORATE, _a._ Not pierced through; also, closed up (said chiefly of the nostrils).

IMPLACEN´TAL, _a._ Having no placenta. Birds are _implacental_.

INCISED´, _a._ Cut out; cut away.

INCUBA´TION, _n._ Act of setting on eggs to hatch them.

INCUM´BENT, _a._ Depressed or bending down upon something; laid at full length; chiefly said of the hind-toe when its whole length rests on the ground or other support, owing to its low insertion on the level of the rest. (131.)

IN´CUS, _a._ A bone of the inner ear of mammalia, held by high authority to be homologous with the _os quadratum_ of birds (which see). See also MALLEUS.

IN´DEX, _n._ The principal digit of the wing is often so called, but is really homologous with the third or middle finger of mammals; the pollex or so-called thumb of birds being the homologue of the mammalian index.

IN´DOLES, _n._ Natural disposition.

INDUMEN´TUM, _n._ Covering of birds; the ptilosis or plumage. (142.)

IN´FRA- (_in composition_). Below; under; opposite of _supra-_. It is in part synonymous with _sub-_, but refers only, to position, while _sub-_ is of more extensive application.

INFRAMAX´ILLARY, _n._ The under jaw bone, or mandible.

INFRAOR´BITAL, _a._ Below the eye-socket.

INFUNDIBU´LIFORM, _a._ Funnel-shaped.

INFUNDIB´ULUM, _n._ Funnel; name of several different organs.

INGES´TA, _n. pl._ Things eaten; contents of crop or stomach. Opposed to _egesta_.

INGLU´VIES, _n._ Crop or craw. Also used synonymously with _chin_.

IN´GUEN, _n._ The groin; whence the adj. _inguinal_. (Little used.)

IN´GUINAL, _a._ Pertaining to the groin.

INNER TOE, _n._ (127.) In most birds the second is the inner anterior toe; in the trogons, the third or middle toe becomes inner anterior by reversion of the second, which is then inner posterior. In a few exotic kingfishers, the second or inner anterior is rudimentary or wanting. In several birds the hallux or first or hinder toe is reversed, and becomes inner anterior. But in any position the _inner toe_, properly speaking, is the second, that one with only three joints.

INNOM´INATE (_bone_), _n._ The pelvic bone, composed of ilium, ischium, and pubis.

INOSCULA´TION, _n._ Same as ANASTOMOSIS (which see).

INSECTIV´OROUS, _a._ Insect-eating.

INSESSO´RES, _n. pl._ Perching-birds; an order now becoming obsolete.

INSESSO´RIAL, _a._ Relating to perching-birds.

INSIS´TENT, _a._ Said of the hind toe, when its base is so elevated that the tip only touches the ground. (130.)

IN´STINCT, _n._ Imperfect reason; the faculty of doing the right thing without knowing why.

INTEG´UMENT, _n._ A covering or envelope; commonly, the skin.

INTER- (_in composition_). Between; among.

INTERARTIC´ULAR, _a._ Between the joints; in a joint; as, _interarticular_ cartilage.

INTERCOS´TAL, _a._ Between two ribs; as, _intercostal_ muscle, artery, vein.

INTERMAX´ILLARY (_bone_), _n._ Same as PREMAXILLARY (which see).

IN´TERNODE, _n._ Any bone of a finger or toe.

INTEROR´BITAL, _a._ Between the eye-sockets.

INTERRA´MAL, _a._ Between the forks or rami of the lower jaw.

INTERRUPT´ED, _a._ Discontinuous; broken up.

INTERSCAPIL´IUM or INTERSCAP´ULUM, _n._ Region of the upper back between the shoulders. (58.)

INTERSCAP´ULAR, _a._ Between the shoulders. The plural, _interscapulars_ or interscapularies, is used to denote the feathers of such region collectively.

INVAG´INATE, _a._ Sheathed.

INVER´TEBRATE, _a._ or _n._ Having no backbone; an animal without a backbone. Opposed to _vertebrate_.

I´RIAN, IRID´IAN, _a._ Pertaining to the iris.

IRIDES´CENT, _a._ Glittering with many colors, which change in different lights.

I´RIS, _n._ Circular muscular curtain suspended perpendicularly in the eye between the aqueous and vitreous chambers, having a hole in the centre (the pupil). It is of all colors in birds.

ISCHIAT´IC, _a._ Pertaining to the ischium.

IS´CHIUM, _n._ One of the pelvic bones, the hindermost.

-ISH. A suffix, forming an adjective, _usually_ denoting possession of a quality in less degree; especially used for colors; as, _blackish_, not quite black, etc.

ISTH´MUS, _n._ Neck or narrow strip connecting two larger portions of same region, patch of color, etc.

J.

JAW, _n._ See MAXILLA, MANDIBLE.

JEJU´NUM, _n._ Portion of intestine between duodenum and ileum (not definite, and little used).

JU´GAL, _a._ Pertaining to the zygoma.

JU´GAL (_bone_), _n._ Same as _malar_ bone.

JU´GULAR, _a._ Pertaining to the jugulum.

JU´GULUM, _n._ Lower throat; lower foreneck. (53.)

JUNCTU´RA, _n._ Articulation; joint.

K.

KEEL, _n._ Same as GONYS (which see). (22.)

KNEE, _n._ Femoro-tibial articulation. (N. B. The heel-joint, _suffrago_, or tibio-metatarsal articulation, is often improperly called _knee_.) (102.)