284 yei;tebi;ate animals. 



the metatai-sal bone of the great toe being, when present, distinct 

 and rudiiuentary. Tlie upiier jiortion of the taisus is amalgamated 

 with the lower end of the tiliia, to which, theref(.>re, the name of 

 " tibio-tavsus " is often apjilied. The ankle-joint is thus jilaced in 

 the middle <.f the tarsus. In most of the longdegged birds it is 

 by the great elongation of the tarso-nietatarsus that the enormous 

 length of the legs is produced. The tarso- metatarsus is followed 

 below by the foot, which consists in most birds of four toes, of 

 winch three are directed forwards ami one backwards. In no wild 

 Birds are there more than four toes ; but some domesticated varie- 

 ties possess a fifth. In all liirds with fcjur toes, the toe which is 

 directed backwards (the great toe or "hallux") consists of two pha- 

 langes ; the innermost of the three forward toes has usually three 

 phalanges, tlie ne.xt has fi.nr, and the outermost toe is composed 

 of five. In many Birds, such as the Parrots, the outer toe is turned 

 backwards, so that there are two toes in front and two behind. In 

 the Swifts, again, all the four toes are turned forwards. In many 

 of the Swinnning Birds (Xntntorcx) tlie hinder toe is wanting or 

 rudimentary ; and in the t)strich both this and the next toe are ab- 

 sent, so that the foot consists of no more than two toes. 



Tlie digestive sj'stem in Birds consists of the beak, tongue, gullet, 

 stomach, intestine, and cloaca, with certain accessory glands. There 

 are no teeth, and the beak is employed, in ilifferent liirds, for holding 

 and tearing the prey, for prehension, for climbing, and in some ca.ses 

 .as an organ of touch, being in these last instances more or less soft, 

 and suiijilied with nervous filaments. In many Birds, too, the base 

 of the bill is surniunded by a eiicle of naked skin, constituting what 

 is called the "cere," and this too serves as an organ of touch. The 

 tongue of birds can r.arely be looked upon as an organ of ta.ste, since 

 it is gener.illy eased in horn, like the mandibles. It is principally 

 cmployeil .-is .in organ of prehension, but it is soft and fleshy in the 

 Parrots, ;iiid in tliein, d<iubtless, acts as an organ of taste. Salivary 

 glands are always ]iresent, but they are r.arely of large size, and are 

 often of extremelj- simple structure. In accordance with the length 

 of the neck, the gullet is usually very long in birds, and is generally 

 veiy dilat.able. In the tle.sh-eating and grain-eating Birds the gvdiet 

 is (lilateil (fig. i'Oo, c) into a pouch which is called the "crop," and 

 is situated in the lower ]iart of the nerk, just in front of the merry- 

 thought. This lu.-iy be simply .-i dil.itatinn of the tube of the gullet, 

 or it may lie a single or double pouch. 1'lie function of the crop is 

 to detain tln^ food, for a, loiigi'r or shorter ]>eriod according to its 

 nature, bcf..re it is sulimittcd to the action of the ]iroper digestive 

 organs. Fii the Pigeons, the fciud \\ liirh hasbi'cii ]ireviiiuslv softened 

 in the cioji is returned to Ihi' mouth, .and supplied to the young in 



