File:The bird, its form and function (1906) (14732610466).jpg

Identifier: birditsformfunct07beeb (find matches)
Title: The bird, its form and function
Year: 1906 (1900s)
Authors: Beebe, William, 1877-1962
Subjects: Birds Birds
Publisher: New York : Henry Holt
Contributing Library: Internet Archive
Digitizing Sponsor: Internet Archive

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n of bone, was evolved. One more fact which may hark back to old, old times,and then we shall leave the past as perhaps trespassingtoo much on the province of the chick while he is yetwithin the egg. Birds (and all the higher classes of ani-mals) have what we may call two separate systems ofnerves, although in some ways they are insolubly con-nected with each other. The brain and spinal cord sendnumerous branches which subdivide into countless nerve-lets, permeating every portion of the body, as we caneasily prove by the feeling, on pricking our skin anywherewith a needle. This is the principal nervous system ofback-boned animals, and it is by this that birds, and allcreatures with well-developed nerves, see, hear, taste,smell, and by which they send messages to the muscleswhen they desire to move them. Below the vertebralcolumn is another lesser system which sends nerves tothe digestive tract and other organs, the movements andfunctions of which are not under control of the will, and
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Fig 144.—Nervous system of Pigeon, showing large eyes and brain, and nervesleading to wings and legs. 197 198 The Bird this is the sympathetic or reflex system. It is a verywonderful thing, this not having to think about the heartbeating or the lungs expanding. We can understand how a muscle (such as the heart)can pump the blood through the body, but we know littleor nothing of the action of nerves. An eagle soars highabove the clouds; a rabbit is discovered crouching ina field far below; the eye of the eagle telegraphs thisdiscovery to the brain; a message is sent along the spinalcord, switches off to the wings, repeats to the muscles,which half close and set the great pinions firmly; theeye is the pilot, never leaving the mark; a triple messagenow goes out, to the wings to hold back, to the legs toreach forward, to the talons to open and clutch! Allis done without a break or hesitation, so quickly thatones eye can hardly register the act, and all by meansof impulses sent through t

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