APPLIED PHYSIOLOGY
CHAPTER I
CELLS
Our body is made of many parts. Its head thinks. Its legs carry it, and its arms and hands take hold of things. The leg cannot do the work of the arm, nor the head do the work of the hand; but each part does only its own work.
1. The simplest animal.—Some animals have parts like a man's; but these parts are fewer. No animal has arms or hands like a man. A fish has little fins in place of legs and arms, while a worm has not even a head, but only a body, and yet it moves. An oyster has only a body and cannot move. The simplest of all animals is very small. A thousand of them would not reach an inch. Yet each is a complete animal. It is called the ameba. It is only a lump of jelly. It can put out any part of its body like an arm and take a lump of food. This same arm can eat the food, too. It can also put out any part of its body like a leg and move by rolling the rest of its body into the leg. It can do some things better than a man can do them, for any part of its body can do all kinds of work. So the ameba grows and moves and does as it likes.
Different forms of an ameba (×400).