Cassell's natural history (1896) (20514875456)

Title: Cassell's natural history

Identifier: cassellsnaturalh03dunc (find matches)

Year: 1896 (1890s)

Authors: Duncan, P. Martin (Peter Martin), 1821-1891; Metcalf Collection (North Carolina State University). NCRS

Subjects: Animals; Animal behavior

Publisher: London (etc) Cassell & Company, Limited

Contributing Library: NCSU Libraries

Digitizing Sponsor: NCSU Libraries

Text Appearing Before Image:

A y ATOMY OF A BIRD.

Text Appearing After Image:

I Kcc'lof Stii "boflv," and others directed forwards and backwards, so as to connect each vertebra with its neigh- bours ; and lastly, a lower arch, the two halves of which are not connected below, but are converted into the more or less long ribs. As these vertebrne are so small it is clear that if their spines were long the free movement of the neck would be greatly impeded, and they are therefore in many cases little more than projecting processes. This free movement is further greatly aided by the characters of the two faces of the body (or centrum) of each vertebra; the face of each is saddle-shaped, that is to say, the anterior face is concave from side to side, and convex from above downwards, while the reverse of this is seen on the posterior face; in addition to this the vertebrse are sejjarated by a disc of cartilage from one another. The region of the neck is, broadly speaking, distinguished from that which succeeds it by the fact that the ribs connected with its vertebrse do not reach to the sternum, or breast-bone. In all birds which are capable of flight this dorsal region has its parts firmly united togetl'.er, and the same holds for the parts which follow, till we reach the region of the tail, where the more anterior vertebra? are movable on one another, so as, perhaps, to serve in aid of the steering organ formed by the rectrices, or feathers (co). In all living birds the caudal vertebrse are a good deal shorter than the body, but Ln the fossil Archwopteri/x they are longer. The only important point to note with regard to the ribs, is the presence on some of them of backwardly directed hooked processes (up, fig. on p. 241), which aid in giving firmness to the thoracic region. The number of ribs is variable, but there is never a large number connected with the dorsal vertebrje, a.s thei-e ai-e in some Carnivora, in Hyrax, and in the Horse. The fore and hind limbs are connected to the body by a series of bones, which form the breast and hip girdles respectively ; with the former series is also connected that large, long bone with its sharply-projecting ridge (/«), which is known as the breast-bone, or sternum, and in the depressions on which so much muscle is collected. Tliis sharply-projecting ridge to the sternum, which is Icnown as the carina, or " keel" (cs), is found only in the flying birds, though here and there, as in the Parrot of New Zealand (Strigops), it is very rudimentary. The lower edge of the bone is often imperfect, so that, as in the fowl, there are two deep clefts on each side, or there may be but a single cleft, an 1 this again maybe converted into a rounded space; in all cases these clefts or holes are covered, or filled by membrane, during the life of the animal. Projecting in front of the sternum, and often intimately connected with it, are the two clavicles (cl), which unite in the middle line to form the bone of child- hood's delight â the furcula, or "merry- thought." Above, this bone is connected with two bones, one of which, called the coracoid (c), descends on each side to fit into a depression on the upper edge of the stermim, while the other, known as the sca- pula, or shoulder-blade (>â (â¢), is set at an angle to the coracoid. The scapula has a, backward and downward direction; while it may be noted that among mammals the coracoid is well developed only in Echidna and Ornitho- rhynchus. These two last bones form, at their point of junction, a cavity into which is fitted the head of the long bone of the arm (wing). In the Ratitse, it must be observed, these two bones are not set at an angle to one another, and they become more firmly united together. As in all the vertebrate animals except fishes, the fore-limb may be divided into three parts (fig. on p. 237)âupper arm, in which there is one bone, the humerus (a); fore arm, in which there are two, radius (d) and ulna (c); and hand (e), which can again be divided into three parts, which in man would be called wrist, palm, and fingers. Now, in some animals the wrist-bones may be ten in

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1896

American Museum of Natural History Library

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