Part 16

One can not do much of anything without tools, so of course the animals have to have them. But because they haven’t sense enough to make tools as we do, or even sense enough to use such tools as they find ready made—pointed sticks and sharp stones and shells and bits of bone and the like—as our very savage and very stupid ancestors used to do, the tools of the animals have to grow on them.

The horse’s front teeth are his mowing machine, with which he cuts down the grass. His great flat-topped grinding teeth that lie in a long straight row along each side of his jaw behind the place where the bit goes, are his millstones with which he grinds his oats and corn into meal. But the cheek-teeth of dogs and cats, which also lie along the sides of their jaws, are not millstones, but knives; and their front teeth, like their claws, are traps to seize their prey and long daggers to stab them with. For the cats and dogs do not grind corn; they kill things. They are butchers, not millers.

In fact, when you come to think of it, nearly all the larger animals are either millers or butchers. Either they grind up plants for food, as horses and cows and sheep and goats do; or else they hunt and kill other living animals and devour them, as do the cats and dogs and wolves and foxes and hyenas and such like. Naturally, these two sorts of creatures have quite different sorts of tools—claws and sharp teeth for one, hoofs and grinding teeth for the other. Tho for some reason or other, pretty much all the animals that are strong enough to do any work, are miller animals. All the horses, oxen, ponies, donkeys, buffalos, elephants, camels, goats, llamas, and I don’t know how many more, that any body can get any work out of, all have hoofs and eat plants. The Eskimo dog, so far as I know, is the only butcher animal that earns a living. The rest just lie round and growl.

So the miller animals have to grind their food. Now millstones have to be kept rough; and as fast as they wear smooth, the miller has to “pick” out the grooves to make them rough again. In like manner, the horses and cows and sheep would soon wear their teeth too smooth to be of any use, if they did not have a way of making them once more rough. In these grinding, millstone teeth, the hard enamel, instead of being on the outside of the tooth as with us, is doubled into folds and plates, and mixed in with the bone of the tooth like the streak of fat and streak of lean in bacon, or like the two colors in marble cake. So the bone wears down faster than the enamel, and leaves the enamel standing up in sharp ridges. Thus the top of the tooth is always rough and ready to do its grinding; and because these teeth are pretty long, an inch or more, they last a long time before they are worn out.

But the dogs and cats, which have teeth like ours, with the enamel all on the outside, soon wear down their teeth so that they will no longer cut. That’s why dogs and cats and the wild creatures like them, are so short lived. They are built to grow up quickly and die young, because there is no use in having them made to live longer than their teeth will hold out. At least that’s one reason Why they don’t live longer.

The elephants have a curious way of taking care of their teeth. They have to take care of them, because the elephants live to be very old—a hundred years—a hundred and fifty—some people say even two hundred. Now a hundred years is a pretty long time for a tooth to keep on grinding leaves and twigs and roots, so the elephant has to save his teeth and make them last.

To begin with, he saves his front teeth by not having any. His two great tusks are two upper front teeth grown out till they are not teeth at all, but crowbars that the elephant uses to grub up roots with. They have no enamel and no root. So they can keep growing at the inner end as fast as they wear off at the outer. Being especially hard bone, they last as long as the elephant does, and get larger and larger as long as their owner lives. After that, they get turned into piano keys and billiard balls.

As the elephant spares his front teeth by not having any, he spares his back teeth by not having many at a time. These are very large, not quite as large as a leg of ham, but quite as large, often times, as a loaf of bread.

The young elephant gets four of these big grinders, one on each side of each jaw, and grinds away on them. After he has used these for a few years and begun to wear them down, four new ones grow just behind the first four. By and by, the first set gets worn out; then the white blood corpuscles take down the roots, the crowns—what there is left of them—fall off, and that is the end of that set. By the time the elephant begins to get old, the second set of four teeth has worn out, and a third set has come in. So a really old elephant has only six teeth—the two tusks, if you call them teeth, and four grinders.

The pigs do something the same. They hold back four very large grinding teeth at the last end of the row, and don’t let them appear till after the front grinders have been pretty well used up. So too do we in a way. We don’t cut our “wisdom teeth” till we are past twenty. Moreover, the wisdom teeth, which are last in the row, and the eight grinders in front of them, two in each half of each jaw, really belong to the milk set which we began to have when we were babies. We don’t need them then. So we hold them back till we do, though that isn’t for twenty years.

The rats, mice, squirrels, beavers, and other creatures that use their front teeth as drills and chisels, have a pretty clever way of keeping them sharp. You can easily see that a squirrel who puts his teeth through the hard shells of nuts every time he gets a meal, or a beaver who cuts through trees six inches across with his, or a mouse or a rat, would use up any ordinary set of teeth in a few weeks, and have to get on as best he could for the rest of his life without any.

The grinding teeth of these creatures are like other grinders, that last till they are worn down—and that’s all. But their four front teeth, two in the upper jaw, two in the lower, are like the elephant’s tusks. They have no roots, and they keep growing out from the inner end as fast as they wear off at the outer. But in order to have them held firmly in the jaw, having no roots, these front teeth start way in at the back of the jaw close to the roots of the last grinders. They grow out along the whole length of the jaw bone, past all the other teeth, and come out at the front of the mouth. So the front cutting teeth of mouse or rat or squirrel are about as long as his legs, and start back almost to his neck. Besides this, they have the hard enamel all in one plate at the front of the tooth, instead of over the entire outside as we do. Then as the tooth wears down, the bone wears fastest and leaves the enamel as a cutting edge, always sharp.

The wild pigs do much the same thing with their four tusks. They start them clear round at the back of the jaw, curve them past the rest and bring them out at the sides of the mouth. Then they put two together to make a tusk, and each grinds on the other and keeps it sharp. But I don’t think that any animal ever does this sort of thing with more than four teeth. He can make four grow all the time, or two as the elephants do, or none. But the rest have to have ordinary roots, and when they wear out, why that’s the end of them.

But the sharks grow several rows of teeth at once, starting them inside the mouth and letting them slide over the jaw in the skin. These are not real teeth set in the bone, but only a sort of skin teeth; and the shark grows them by the dozen, new ones as fast as the old drop out. The snakes do much the same thing with their poison fangs, and keep always at least one new pair folded down behind the old ones, ready when these get pulled out. But snakes and sharks don’t chew with their teeth, they only bite with them.

Now let’s see if you can’t find out for yourselves how it is that pussy cat keeps her claws as sharp as needles. You can clip off the points, but it will not be many days before she will make new ones, just as sharp as the old. If you study the claw you will see how she does it. The dog has the same device, only his nails are not so sharp.

XLVIII

Why The Blood Is Salt

The blood is really salt. So is the sweat, as you can easily prove by putting your tongue anywhere on your skin, after you have been hot and sticky for a long time. And of course the tears are salt, as no doubt you found out long ago, sometime when everybody was especially horrid and they ran down into your mouth. In fact, pretty much everything about the body is salty, for the reason that it is all made of blood, which is itself pretty salt.

Now the blood is salt because the sea is. I much suspect that if the ocean had always been fresh water, like the ponds and lakes, then our blood, and the blood of all other animals, and all sweat and tears and the like, would have been fresh also. For the sea and the blood are salt with the same kinds of saltness. Their salt is mostly the sodium chlorid which we use for table salt, and besides these, there are calcium which makes limestone and lime and mortar and plaster, potassium which makes potash and soft soap, and various other metals including even gold. Altogether, sea water and blood are extraordinarily alike, especially when you consider that there are vast numbers of little animals in the sea that one can’t so easily tell from the white corpuscles of the blood.

The reason for all this is that the simpler creatures of the ocean do actually use the sea water for blood. Instead of having their bodies shut up tight as we land animals have ours, so that nothing gets into them unless we breathe or swallow, the inside of their bodies is open to the sea water, and the sea water flows in and out freely.

The sponges are like this. They take the water in through their smaller holes, and let it out through the large ones. They breathe the air that is in the water, and they turn their waste matter back into the water again, just as if the water were their blood. Many other creatures manage in this way, getting along without any private blood of their own, and using the great common ocean instead.

The rest of us have simply shut up our bodies and caught a little bit of the ocean inside. We call this bit of ocean, blood; and we have added various things to it. But still it is sea water, the same old sea water that is the blood of the earth and of all the lowly sea creatures that have no private blood of their own.

There are a great many other things also that we big land creatures have and do for no other reason than that some small sea creature began that way, and there has happened to be no special reason why anybody should change.

For example, all fishes, as you know, breathe by taking water in through their mouths and letting out again through a set of slits, usually five in number, at the side of what would be the neck if the fish had one. When the little fish is forming in the egg, at first it does not have any of these “gill slits” and so has to breathe through its skin. By and by, however, after the lower jaw has formed and there is a mouth, these slits punch through and become the convenient openings that we put a forked stick through when we go fishing and so bring home our fish, instead of putting them in our pockets, which is really a practice not at all to be commended.

So the little fish, while still in the egg, has these gill slits in the side of his head because later, when he gets hatched out and swims round, he is going to use them to breathe with. But the little chick in the egg, after his lower jaw has begun to grow, also has these same gill slits in the side of his neck, although when he hatches out, he is going to breathe with lungs, and is never going to have the least use for gills. So, too, do little puppies and kittens and colts and calves and all the land animals that breathe with lungs and haven’t the slightest use for any such holes.

Sometimes the hole doesn’t even break clear through. It starts from the inside and comes out, and from the outside and goes in, but the two tunnels never quite meet, and the hole never gets really open. But whether the holes open through or not, they soon close up again, and leave no sign that they have ever been there at all.

All except the first hole on each side, the one nearest the mouth. That never closes again, but remains open and becomes the hole into the ear. There is a hole in from the outside, as you know, the one you used to put beans and pencils in, only you oughtn’t. And there is another hole from the inside, beginning high up in the throat just where you can’t see it, and running in till it almost joins the other hole. Between the two is just a thin skin, which is the “drum” of the ear, and if you get a hole in it you may never be able to hear again. Because this drum never grew. It is the place that remained after one tunnel came in from outside, and another from inside, and the two didn’t quite meet.

So it comes about that all of us land creatures with backbones, who breathe with lungs, start making gill slits which we can’t possibly use. Then, because we have them on hand, we use the one farthest in front for the hole of the ear, and close the rest up again. And we take all that trouble—though it doesn’t trouble us much at the time—just because various other backboned creatures, which live in the water and don’t have lungs, had to make gill slits to breathe with.

There are a lot of things of this sort—parts and organs and members which one creature, while it is in the egg, makes and doesn’t use, just because some other creature, when it grew up, had to have them. You know what a short tail a hen or a turkey or a pigeon has—just a stub of a tail, only just big enough to stick its tail feathers in. But a little hen or turkey or pigeon, while it is still in the egg, has a tail like other animals, long enough to wag.

There is a kind of salamander, which is unlike most salamanders, efts, newts, and the like—these are all pretty much the same thing, and you find them almost anywhere in the brooks and the ponds and the damp woods. All of these that you are ever likely to see breathe with gills like a fish, and can live in the water. Only instead of having their gills covered over with a bony plate like the fish, these creatures often have them outside, like a sort of lace collar that hangs down at the side of their necks. Tom, the chimney sweep, in Charles Kingsley’s famous tale, after he turned into a water baby, had just such tufted gills so that he could swim under water like any newt or eft, and if you haven’t read “The Water Babies,” it’s certainly high time you did.

What I started to say is that this particular kind of salamander lives on the land. So he doesn’t need gills and doesn’t have them. But the little salamander, while he is still in the egg, has gills like any salamander, though for all the use he can ever put them to, he might just as well have been furnished with a pair of skates; for by the time he hatches out of the egg, the gills have been taken to pieces by his white corpuscles and the stuff used to make some other part of the body.

All the same, if you break open the egg, take the little creature out, and put him in the water while he still has gills, he will swim away, and live under water as well as any water creature. But if you wait till he hatches out of himself and has lost his gills, then if you put him in the water, he will drown just as you would. So the little salamander, that is going to spend his life on dry land, still has gills while he is in the egg and has no use for them, all just because other salamanders that live some of the time in the water need gills to breathe with.

Then there are the snakes, which have lungs and breathe air like any land animal. Only a snake is so very slender that there isn’t room in him for two lungs side by side. So he has only one proper lung, very long and thin, that runs from his neck pretty well down to his tail. Nevertheless, the snakes still keep the other lung, small and quite useless, tucked away beside the front end of the one they do use. Other reptiles have two lungs, so the snakes have to have two lungs also, though they can’t possibly use them both, and the other which they don’t use, merely takes up room.

We human beings are just as bad as the rest. Every little while, somebody comes down with appendicitis and has to be taken to the hospital to have his “vermiform appendix” taken out. The appendix isn’t the slightest use to anybody, we are better off without it, but in cows and dogs and rabbits and kangaroos, and various other animals, especially those that eat grass and leaves, it is a good deal of use for helping to digest food. So we have to have it, to be like the rest—and then pay the doctor to cut it off.

We don’t move our ears as horses and dogs and rabbits do. But still the muscles are there; and people say that anybody who wanted to take the trouble could learn to wag his ears like a baboon. Anyhow, the muscles are there, though we don’t use them and other creatures do.

We are said to have no fewer than one hundred and eighty such useless things about us—all sorts of little things that are no use to us at all and no use to half the animals that have them. But they are useful to the other half, and we all have to be in the fashion. Among these is a strange sort of single eye, set in the middle of the head, so that we really have three eyes instead of two. Our third eye is no bigger than a pea, and it lies tucked away between the two sides of the brain, well inside the skull, where it cannot possibly see anything. All the four-footed creatures have it. But in none of them is it the slightest use, except in certain lizards, especially in one in New Zealand, where it is a real eye placed in the middle of the forehead between the other two. Several American lizards also have this extra eye, though it isn’t good for much seeing, among them the “horned toad” of California, which of course isn’t a toad at all. So, just because a few lizards want three eyes to see with, the rest of the four-footed animals and we human beings have to have an extra eye that we don’t want, tucked away in pitch darkness inside our heads.

But that’s the way things are managed—salt blood, and gill slits, tails and gills in the egg and not out, extra lungs for the snakes, and extra eyes for us all, like Little Three Eyes in the story. It’s like the extra legs and tails on the lizard, and the extra heads on the planarian. Nature gets started making things, and doesn’t seem to be able to stop.

XLIX

Horses’ Fingers

The horse does have fingers—as one can easily see by counting up the parts of his legs. Let’s start with the fore-leg, and begin at the top next the body.

The sharp ridge just in front of the place where the saddle goes, between that and the beginning of the mane, is mostly backbone, the same part that we feel under our coat collars at the backs of our necks. The horse’s shoulders, against which the collar rests when he pulls his load, are mostly shoulder-blades, for the chest of all four-footed beasts is narrow, and the shoulder-blades, instead of being on their backs, as ours are, are at their sides. The upper arm, between the shoulder and elbow is short, and is buried in muscle so that one doesn’t notice it. So the first joint that shows, where the fore-leg joins the body, is not the shoulder but the elbow. The upper half of the arm is inside the skin.

The upper half of the horse’s fore-leg, then, is our fore-arm, between elbow and wrist; and sure enough, that bone in the horse is double just as it is in us, and in all animals that can twist their hands round, tho the double bone isn’t the slightest use to the horse. What we call the horse’s knee, then, is his wrist—and again, like our wrists, it has a lot of little bones which make our wrists supple so that we can bend them in all sorts of ways, but which also are no use at all to the horse.

Then there is the horse’s shin—which isn’t shin at all, but the palm-bone of the middle finger, which in us runs from the wrist to the knuckle. The rest of the leg is the middle finger, with the proper three joints, which every finger ought to have, and a gigantic finger nail, which is the hoof. So the horse has a hand, and a very large hand too; only he has lost all his fingers except one, so that he really stands up and runs on the nail of his middle finger. Nevertheless, the horse hasn’t quite lost the rest of his hand; because along the sides of this middle-finger-palm-bone, which we call the shin, lie two other little bones, too small to be any use, which are the palm-bones of the first finger and the third. But once in a long while a colt is born with two little hoofs on these bones, so that it has three fingers instead of one. The rhinoceros, on the other hand, has three fingers, all nearly the same size; while the elephant keeps all five.

Now if you will notice the fore-leg of a cow, you will see that it is just about like that of a horse, till you get down to the wrist. Below that point, the cow, instead of having one palm-bone and one finger, has two. Of course, then, it has two finger nails. The deer has two fingers like the cow, and then two little ones besides, and so does the pig. But the hippopotamus has all four fingers and lacks only the thumb.

All of which, if you keep your eyes open, you can make out for yourselves and more. Only I wish somebody would tell me why all the animals that have horns at the side of their heads—cows and sheep and goats and deer and buffaloes and I don’t know what all—have either two fingers or four; and why the creatures that have one finger, or three fingers, or all five, never have such horns. That is something that nobody has yet been able to find out.

So much then for the horse’s hand—and what a whacking big hand it would be, by the way, if it did have all five fingers instead of only one! Let’s see what we can make out about the horse’s foot.

The thigh, as you can easily make out when the horse moves, starts close up to the tail, and like the upper arm, is almost wholly inside the skin. So the first joint that shows is the knee, and the great muscles which, as you sit behind to drive, you see pulling you along so strongly, are those of the calf of the leg. The joint that comes nearest the driver’s feet, which we call the gambrel, is then the heel. It certainly does look like a heel; and the rest of the leg is the middle one of the five long bones of the foot, with the middle toe on the end of it. So the horse stands on the end of his middle toe, and his hind hoof is his middle toenail.

The cow, of course, keeps two toes with their foot-bones. The dog has four. I don’t think a dog ever puts his heel down so as to stand on the whole flat of his foot, except sometimes when he stands up to beg. But cats and rabbits often do, when they want to stand up on their hind legs to see as far as possible. Still they don’t do it enough to have soles to their feet all the way back to the heel. But the bears and the monkeys and a lot of other animals that can’t run very fast, do put the whole foot down on the ground, and do have a sole all the way back to the heel. In general, the faster an animal can run, the more it stands up on its fingers and toes, the longer its feet and hands are, the shorter its thighs and upper arms, and the fewer fingers and toes it has. That’s why the horse, which I suppose is about the fastest animal there is, has his fore-leg at least half hand, and his hind leg mostly foot.