. The bird; its form and function . d frayed near the tip,forming delicate brushes—efficient instruments either tosuck up nectar or to flick out insects from the heart ofcorollas^^ The Crop From the back of the throat to the stomach extendsa tube, the gullet or oesophagus, through which the food ■ 1— 1/ ii t A^i- ^ 1,^^ ^i^P 1 ll!3 i^? - ^ •■^^E, W S ■ ^^■^■^-;^ ■ ■ #■* w^ |rVfC«aai|^HH^^^^^^H^B K% ^Wf *f l*Sf^ HBHP ^ *. ^^^^^hP^^J ?¥r^ ^^«^^ K^^Cla^B Organs of Nutrition 129 descends after it leaves the mouth. In some birds thisis a simple tube of the same diameter throughout, alwaysmoist from
. The bird; its form and function . d frayed near the tip,forming delicate brushes—efficient instruments either tosuck up nectar or to flick out insects from the heart ofcorollas^^ The Crop From the back of the throat to the stomach extendsa tube, the gullet or oesophagus, through which the food ■ 1— 1/ ii t A^i- ^ 1,^^ ^i^P 1 ll!3 i^? - ^ •■^^E, W S ■ ^^■^■^-;^ ■ ■ #■* w^ |rVfC«aai|^HH^^^^^^H^B K% ^Wf *f l*Sf^ HBHP ^ *. ^^^^^hP^^J ?¥r^ ^^«^^ K^^Cla^B Organs of Nutrition 129 descends after it leaves the mouth. In some birds thisis a simple tube of the same diameter throughout, alwaysmoist from the secretion of (mucous) glands which arefound abundant in its walls, but serving merely as apassage for the food on its way to the stomach. In another class of birds an enlarged chamber ispresent, called the crop. This serves a somewhat simi-lar purpose as the external pouch of the pelican; thatis, it acts as a receptacle for food. No especial digestiveglands are found here, and the only agents acting on. Fig. 102. —Brush, or tube-like tongue of Honey Creeper. Twice natural size. the food are water, the secretions of the salivary glands,and the heat of the birds body. The crop exists onlysuperficially in some birds, the dilation being hardlynoticeable. From these we find a succession of more distinctlymarked permanent crops, until in grain-eating birds thisorgan is very prominent. If we examine an EnglishSparrow after it has made a hearty meal in the chicken-yard, we will find the crop filled with grains of wheat,some cracked in pieces by the bill, others entire. I 30 The Bird When we sought the extreme in the provision of sahvain birds, we had to refer to a swift, h\ing in caves inislands of the Malay Archipelago, but to find the highestdegree of development of crops is a much easier the ordinary pigeon the crop is of very great sizeand divided into two lobes. The capacity of the cropin some birds of this class is astonishing. As many as
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbirds, bookyear1906
