Animals are much stronger and much better able to take care of themselves when they come into the world than babies are, and after they are born they grow up much more quickly than babies do.
Animals can use their legs earlier than babies can. A colt or a calf can stand on its feet on the same day on which it is born. The giraffe can stand up within twenty minutes after it has left its mother's body. But most babies cannot stand before they are a year old.
Young animals can eat the same things that grown up animals eat long before babies can eat the things that grown up people eat. As soon as babies are born they are fed with milk from their mothers' breasts. If a mother cannot feed a baby with her own milk she uses the milk of the cow and for nearly a year milk is the chief food of the baby.
The animals that grow up in the bodies of their mothers are fed with milk by their mothers in the same way that babies are fed. We call these animals mammals. Mice, lions, dogs, cats, men, women, are mammals. The name is easy to remember because it sounds so much like
