. The bird; its form and function . Fig. 153.—Brown Thrasher with eyes wide open. thing about them was the great size of their eyes—meas-uring as much as twelve and fourteen inches orbits were surrounded by a series of bony plates,and in certain birds of to-day we find a similar circle ofsmall overlapping bones. To make the simile between a camera and an eye holdgood, we must show that the latter is provided with a The Senses 213. Fig. 154. —Brown Thrasher with nictitating membrane drawn. \» r ^ ^ ^^^iyji r \ ^ Fig. 155.—Same with eyelids closed. 214 The Bird shutter, and in fact
. The bird; its form and function . Fig. 153.—Brown Thrasher with eyes wide open. thing about them was the great size of their eyes—meas-uring as much as twelve and fourteen inches orbits were surrounded by a series of bony plates,and in certain birds of to-day we find a similar circle ofsmall overlapping bones. To make the simile between a camera and an eye holdgood, we must show that the latter is provided with a The Senses 213. Fig. 154. —Brown Thrasher with nictitating membrane drawn. \» r ^ ^ ^^^iyji r \ ^ Fig. 155.—Same with eyelids closed. 214 The Bird shutter, and in fact our bird has not one, but three—eyeUds we call them. So between winks all day ourbird is taking snapshots, inconceivably more perfect andcontinuous than any cinematograph ever produced. Wehave but two eyelids, and ever}^ time we wink theseshoot toward each other, moisten the surface of the eye-ball, clear it of dust, and are back in their places so quicklythat we are not aware of any interruption of our upper lid has most to do with covering the eye. Inalmost all birds this condition is unusual and the lowerlid comes far upward over the eyeball. Perhaps the mostnotable exception to this is among the Great Horned Owls,where the action of the two lids is like that of our own. When birds are sleepy these lids close, but usuallyin winking, the third eyelid, or nictitating membrane, aloneis drawn across the eye. This lid i
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbirds, bookyear1906
