Animal life in the sea and on the land . ure of birds is104° ; that of the human body is 98°. 16. The Music of Birds.—The ex-quisite music of the birds is producedby an arrangement of bones and car-tilages at the lower end of the wind-pipe, or trachea, as it is called. Cur-rents of air passing through this partof the trachea give a quivering motionto the membrane stretched across it,and produce all the varied notes sopleasing to our ears. 17. Birds evidently sing sometimesfor their own pleasure, and then the whole depths of theirnature seem to be poured into their music; but their songis also
Animal life in the sea and on the land . ure of birds is104° ; that of the human body is 98°. 16. The Music of Birds.—The ex-quisite music of the birds is producedby an arrangement of bones and car-tilages at the lower end of the wind-pipe, or trachea, as it is called. Cur-rents of air passing through this partof the trachea give a quivering motionto the membrane stretched across it,and produce all the varied notes sopleasing to our ears. 17. Birds evidently sing sometimesfor their own pleasure, and then the whole depths of theirnature seem to be poured into their music; but their songis also at times a call to their mates and to their youngones. As a rule, male birds are more musical than theirmates. They are likewise larger and more brilliant. 18. Their Coloring. — Gayest of all the birds are thoseliving in the tropics, while those that inhabit the Arcticregions are of dull colors, and some of them change towhite when winter comes and the ground is covered withsnow. So birds, too, you see, also resort to mimicry. 11*. Fig. 164. — Plan ofCirculation inBirds and Mam-mals. a, right auricle ; b, leftauricle; c, c, ventricle. 250 ANIMAL LIFE IN THE SEA AND ON THE LAND. 19. Their Plumage.—Birds are the only animals that areclothed with feathers, and much of their beauty is due tothe colors and markings of this soft, fluffy covering aswell as to its charming metallic lustre. 20. Growth of the Feathers.—These beautiful feathersgrow from little sacs in the skin, and are made of a hornysubstance, much the same as the scales of reptiles. But,unlike these scales, the feathers have split up, duringgrowth, into many narrow strips, which give them theirpeculiar softness. Upon the legs and feet of most birdsyou may see scales which have not split up thus intofeathers. 21. Feathers examined.—You may also notice how differ-ent the soft, downy feathers, overlapping one another so asto form a warm covering for the body, are from the largequill-feathers of the tail and w
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1887
