You have seen puppies fall out in the same human fashion, and kittens also, and older folk as well. I have seen a game of wood-tag among friendly gray squirrels come to a finish in a fight. As the crows pass over during the winter afternoon, you will notice their play--racing each other through the air, diving, swooping, cawing in their fun, when suddenly some one's temper snaps, and there is a mix-up in the air.
They can get angry, but they cannot laugh. I once saw what I thought was a twinkle of merriment, however, in an elephant's eye. It was at the circus several years ago. The keeper had just set down for one of the elephants a bucket of water which a perspiring youth had brought in. The big beast sucked it quietly up,--the whole of it,--swung gently around as if to thank the perspiring boy, then soused him, the whole bucketful! Everybody roared, and one of the other elephants joined in with trumpetings, so huge and jolly was the joke.
The elephant who played the trick looked solemn enough, except for a twitch at the lips and a glint in the eye. There is something of a smile about every elephant's lips, to be sure, and fun is so contagious that one should hesitate to say that he saw an elephant laugh. But if that elephant didn't laugh, it was not his fault.
From the elephant to the infusorian, the microscopic animal of a single cell known as the paramoecium, is a far cry--to the extreme opposite end of the animal kingdom, worlds apart. Yet I have seen _Paramoecium caudatum_ at play in a drop of water under a compound microscope, as I have seen elephants at play in their big bath-tub at the zoölogical gardens.
Place a drop of stagnant water under your microscope and watch these atoms of life for yourself. Invisible to the naked eye, they are easily followed on the slide as they skate and whirl and chase one another to the boundaries of their playground and back again, first one of them "it," then another. They stop to eat, they slow up to divide their single-celled bodies into two cells, the two cells now two living creatures where a moment before they were but one, both of them swimming off immediately to feed and multiply and play.
Play seems to be as natural and as necessary to the wild animals as it is to human beings. Like us the animals play hardest while young, but as some human children never outgrow their youth and love of play, so there are old animals that never grow too fat nor too stiff nor too stupid to play.