. The bird, its form and function . om the under surface ofthe drum. This is the columella, or little column ofbone, and will have an interest for us later on. If we examine the way in which the upper and lowermandibles or jaws are joined to the skull, we will find avery ingenious arrangement; one very different fromthat in ourselves. If the beak of a bird is to serve ashand, lips, and mouth, it must be as free and movable aspossible, and instead of the upper jaw being fixed im-movably to the skull, and the lower jaw swinging upand down from it, we find that the upper jaw is attachedvery loose
. The bird, its form and function . om the under surface ofthe drum. This is the columella, or little column ofbone, and will have an interest for us later on. If we examine the way in which the upper and lowermandibles or jaws are joined to the skull, we will find avery ingenious arrangement; one very different fromthat in ourselves. If the beak of a bird is to serve ashand, lips, and mouth, it must be as free and movable aspossible, and instead of the upper jaw being fixed im-movably to the skull, and the lower jaw swinging upand down from it, we find that the upper jaw is attachedvery loosely, while each side of the lower mandible hingesupon a loose irregular-shaped bone, known as the quad-rate. A long slender bone connects the quadrate with I lo The Bird the upper mandible, which bone we may call the when we come to look closely at the quadrateswe find that they are very important, and in addition tosupporting the bar of bone from the upper jaw, andpivoting the lower jaw, they bear another pair of bones. Fig. 85.—Columella in ear of Snowy Owl (magnified 2 diameters). extending inward from them, beneath the skull, to thebroad thin palate or roof of the mouth. In a chicken the individual movement of the upperjaw is not very great, but in some birds, such as parrots,it is much more noticeable. With a sharp knife we canentirely detach the upper and lower jaws of most birds,without cutting through a bone, the connection consist-ing only of exceedingly tough tendons. When we foundour sharks skull we perhaps wondered what had become The Skull III of the jaws with the many rows of teeth, and we maynow guess that they were attached so loosely to the skullthat the action of the water washed them away withthe flesh. This was the case, and in all fishes we findboth jaws as separate bones. Among reptiles we findthe quadrate bone free onh in snakes, an admirableadaptation which enables them to swallow their preyentire. The bones forming the palate, or roof of t
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