File:The bird; its form and function (1906) (14568929778).jpg

Identifier: birditsformfunct01beeb (find matches)
Title: The bird; its form and function
Year: 1906 (1900s)
Authors: Beebe, William, 1877-1962
Subjects: Birds
Publisher: New York, Holt
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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to lubricate it. This is accomplishedby certain glands, some beneath the tongue, others situ-ated in the upper portion of the mouth. These are notfound in fishes, nor in other creatures which live alto-gether in the water; but in reptiles several groups aredistinguishable. In birds they vary greatly, some havingscarcely a trace, while others have large well-developedglands. Salivary is the common name given to certainof these, and we will let that name represent all. In ourselves, saliva is an important aid in digestion.Besides moistening the food and softening all hard por-tions, it exerts active chemical effects, as, for example, ii8 The Bird changing starch to sugar and in many other ways makingready the food, that the important changes which takeplace in the stomach may begin at once. In birds, how-ever, the sahva has but little chemical effect on the food,its principal use being to moisten the substances beforethey are swallowed. It is not often that Nature, when she has produced
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Fig. 90 —Nest of Chimney Swift; twigs glued together with sahva. an organ or special tissue by the elaborate synthesis ofevolution, confines its use to any one function. If birdswere provided with salivary glands intended only for thepurpose mentioned above, they soon found other uses forthem. In a woodpecker we will find very large salivaryglands on each side of the mouth. These secrete a stickyliquid which covers the long, many-barbed tongue and isan efficient aid in picking out insects from their holes inthe bark and wood of trees. Organs of Nutrition 119 Many birds carry in their beaks the grasses andtwigs with which they construct their nests, and if a stickyfluid helped them to get their food, why would it notalso soften the twigs and make them easy to bend? Notonh this, but certain birds, such as our Chimney Swifts,are provided with saliva in such quantities, and of suchtenacious consistency, that the entire nest—a mosaic of

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