By this means they also get rid of the necessity of staying rooted in one place, to suck up moisture and food from the soil.

One of the chief and most striking differences between plants and animals is that animals have mouths and stomachs, while plants have not.
THE DIGESTIVE SYSTEM How the Food Reaches the Stomach.

Our body, then, has an opening, which we call the _mouth_, through which our food-fuel can be taken in.
A straight delivery tube, called the _gullet_, or _esophagus_, runs down from the mouth to a bag, or pouch, called the _stomach_, in which the food is stored until it can be used to give energy to the body, just as the gasoline is stored in the automobile tank until it can be burned.
The mouth opening is furnished with _lips_ to open and close it and assist in picking up our food and in sucking up our drink; and, as much of our food is in solid form, and as the stomach can take care only of fluid and pulpy materials, nature has provided a mill in the mouth in the form of two arches, of semicircles, of _teeth_, which grind against each other and crush the food into a pulp.
[Illustration: THE FOOD ROUTE IN THE DIGESTIVE SYSTEM In this diagram the entire alimentary canal is shown enlarged, and the small intestine greatly shortened, in order to show distinctly the course of the food in the process of digestion.] In the bottom or floor of the mouth, there has grown up a movable bundle of muscles, called the _tongue_, which acts as a sort of waiter, handing the food about the mouth, pushing it between the teeth, licking it out of the pouches of the cheeks to bring it back into the teeth-mill again, and finally, after it has been reduced to a pulp, gathering it up into a little ball, or _bolus_, and shooting it back down the throat, through the gullet, into the stomach.
The Intestines.

When the food has been sufficiently melted and partially digested in the stomach, it is pushed on into a long tube called the _intestine_, or _bowel_.

During its passage through this part of the food tube, it is taken up into the veins, and carried to the heart.