Page:Popular Science Monthly Volume 17.djvu/621

From Wikisource
Jump to navigation Jump to search
This page has been validated.
603
HOW ANIMALS DIGEST.

ing the huge mouthful down its throat. But how shall the act be accomplished with no limbs to assist? As the under jaw divides in front, and articulates with the skull by the intervention of extra movable bones, the mouth and throat can stretch enormously. The sharp, conical teeth are recurved, acting like the barb of an arrow to hold whatever position is gained. Each side of the jaw is pushed forward in turn and gains a new and further hold on the carcass, which by successive slight movements is slowly pulled head first down the gullet. The common striped snake seizes a toad or frog, however he can catch him, usually by one or both hind legs, and immediately proceeds to "take him in," despite all protests and struggles.

PSM V17 D621 Skull of a serpent.jpg
Fig. 2.—Skull, of a Serpent (Python): b, articular portion of the lower jaw; a, quadrate bone; c, squamosal portion of the temporal bone.

As the opposite of the enormous throat of the snake, the bulky whalebone whale has the smallest throat, proportionate to its size, of any animal just large enough to admit the tiny creatures which are its food. We see in this a fine example of Nature's economy.

The alligator has a curious way of preventing the admission of water when swallowing prey. Seizing a fish or other small creature, the reptile rises to the surface of the water and flings it into the air; then, before it reaches the water, catches it and gulps it down. If the prey is too large to handle in this manner, it is carried to the shore to be devoured.

Ingluviation.—Many animals can not procure their particular food at all times. Such either can endure fasting, like members of the cat tribe, or have a special reservoir, as shown in the crop of a fowl. This crop is only a dilatation of the gullet. In the cormorant, the whole gullet is very capacious, for the purpose of storing fish; on account of which habit the bird has become a type of voracity. The pigeon has its crop divided into two—perhaps to give a better form for flight. The pelican has a bag beneath the lower jaw. Many small animals, insects especially, have crops. Similar in purpose is the first stomach, or paunch, of a cud-chewer. Birds which eat fruit, insects, or other food readily procured, and of a character which needs no delay in digestion, have usually no crop, or but a rudimentary one.