[Illustration: VENUS'S FLY-TRAP.]

~2.~ But we have yet to learn the most curious thing about this strange
plant, which seems to act so much like an animal. If we open the leaf
after a few days, it will be found that the fly has almost entirely
disappeared. The fly has not escaped, but it has been dissolved by a
fluid formed inside of the trap, and the plant has absorbed a portion of
the fly. In fact, it has really eaten it. The process by which food is
dissolved and changed so that it can be absorbed and may nourish the
body, is called _digestion_ (di-ges´-tion).

~3.~ The Venus's fly-trap has a very simple way of digesting its food.
Its remarkable little trap serves it as a mouth to catch and hold its
food, and as a stomach to digest it. The arrangement by which our food
is digested is much less simple than this. Let us study the different
parts by which this wonderful work is done.

[Illustration: THE DIGESTIVE TUBE.]

~4. The Digestive Tube.~--The most important part of the work of
digesting our food is done in a long tube within the body, called the
_digestive tube_ or _canal_.

~5.~ This tube is twenty-five or thirty feet long in a full-grown man;
but it is so coiled up and folded away that it occupies but little
space. It begins at the mouth, and ends at the lower part of the trunk.
The greater part of it is coiled up in the abdomen.

~6. The Mouth.~--The space between the upper and the lower jaw is called