Part 13
Did you ever stop to think why you are sleepy when night comes? You play hard all day, running about until your legs are tired enough to drop off. By and by, you begin to be sleepy, an hour or two it may be before your proper bed time. You are tired in your legs. But you are sleepy in your eyes. Your legs are not sleepy in the least; and your eyes are not tired. How did the eyes find out that the legs had been running hard and needed sleep?
It is these same waste matters in the blood. We run our legs off by day; and by night time a hundred thousand little explosions in our muscles have used up so much sugar and the rest, that the blood is filled with the waste material, and the lungs cannot carry it off.
So it stays in the blood and poisons us—not badly, but just about as much as if we had taken a small dose of laudanum or alcohol or any of the large number of sleepy poisons, which kill one by putting him to sleep so hard that he cannot wake up. Our “fatigue toxins” as we call them (which is simply Latin for poisons that we make by getting tired) poison us just enough to make us sleep. While we sleep we don’t do much; less of these toxins are formed; the lungs and kidneys have time to catch up with their work; pretty soon the blood is clear again, and we wake up in the morning ready to do it all over once more. We are made to stand a certain amount of poisoning, and get over it. The trouble comes when we poison ourselves With things that we put into our blood, that we might have kept out.
Did you ever think why, after you have been running hard for a long time, your legs ache? Or why they stop aching when you sit down to rest, but don’t stop at once? It is these same fatigue toxins. You explode your muscle cells faster than the blood can wash away the products of the explosions. So these accumulate. By and by, they begin to poison the muscle, and you begin to feel the pain. If you keep on working, as people have to sometimes in spite of weariness, the ache and the poisoning gets worse and worse, till the muscle simply refuses to work any longer.
If you stop to rest, the ache of weariness still continues. But after a little, the blood stream washes the muscle clean. Then the ache is gone, and you can get up and run again. Nevertheless, a whole day’s play or work will so load up the blood with toxins that it can no longer wash the muscle clean. Then you must take a longer rest, go to sleep, and give time for the blood itself to clean up.
Perhaps you have noticed (if you haven’t, try it—only don’t lie on the damp ground) that when your legs are tired, they rest and stop aching much more quickly if you put your feet up higher than your head. This is, of course, because the blood current coming from the tired muscles, can run down hill, and so most easily drain off the toxins which make the ache. So too, you can keep fresh much longer, whether you are working or playing with the muscles, or sitting still and working your brains over your lessons, if you stand up properly and don’t slouch. When you slouch, you cramp your lungs. The cramped lungs fail to clear the blood. The dirty blood fails to wash brain or muscles clean, and you get tired sooner than you ought. For the same reason, you tire more quickly in bad air. But if you give blood and lungs a fair chance, they will do a lot of resting for you while you are still at work.
But long before we get in the least tired, we get out of breath. Poisons as before, only this time it is largely the carbon dioxid that does the business. The muscle-sugar explodes, and forms the carbon dioxid. The carbon dioxid leaks out into the blood; and the blood, circulating thru the body, carries it to a certain nerve center high up in the back of the neck. This in a sense tastes the carbon dioxid, something as the tongue tastes it in a glass of soda water.
When the nerve center in the neck tastes a little carbon dioxid, it doesn’t say anything. But the moment the taste begins to get strong (which is in less than a quarter minute after one starts running hard) it telephones over the nerves to the lungs: “Here, here, here! What is the matter with you fellows. Get busy. Breathe hard. This blood is fairly sizzling with burnt up sugar!”
Thereupon the lungs get down to work. They breathe as hard and as deep as they can; while the heart, which has also been telephoned of the situation, beats harder and harder, to give the lungs all the blood they can clean, and the working muscles all the blood they can dirty.
If heart and lungs hold their own, nothing in particular happens. But if we keep running on too hard, so that muscles poison the blood faster than the lungs can un-poison it, then the nerve center which is in the back of the neck interferes once more. When it cannot make heart and lungs work faster, it calls off the muscle. Suddenly it gives us such a feeling of loss of breath and suffocation, that we simply cannot run another step. We have to stop. Then heart and lungs catch up on their work.
Curiously enough, getting one’s “second wind” as we say, when the lungs after pumping violently, settle down to working steadily once more tho we still keep on running, and “getting in training” so that we can do all sorts of exercises without getting winded, both these highly desirable conditions depend in part on teaching this “respiratory center” in the neck not to raise so much of a row when it smells a little carbon dioxid in the blood. We train our muscles to do their work; and we also train this nerve center not to get rattled and turn on that feeling of suffocation until it absolutely has to. We get it used to burnt muscle-sugar so that it doesn’t mind the taste as it did.
So, as I say, we live only by just escaping being mildly poisoned. But the curious thing about it is that among these various poisons which would certainly kill us forthwith, if we did not promptly get them out of our bodies, stands, of all things, sugar.
We eat a good deal of sugar in our food. We make a good deal more out of other sorts of food. If we did not make sugar, and have it always on hand in our blood, we could neither work nor live. And yet thousands of persons, every year, die of nothing in the world but sugar poisoning.
Sugar is so very poisonous that we have a special arrangement in our livers for keeping down the amount that at any one time gets into the blood. But for this, a box of candy, or a meal of bread and potatoes would inevitably kill us within three hours. The blood of a full grown man always contains about a quarter ounce of sugar, that is to say, two ordinary lumps. If he has less than two lumps, he begins to starve. If he has more than three or four lumps, his head feels heavy and he cannot keep awake. He begins, in short, to be poisoned. But any one who should get his blood half as sweet as he takes a cup of tea or coffee, would promptly drop into a sleep from which he would never wake up at all.
One thing then that the liver is for is to catch the sugar as it goes by, after a meal, and store it up where it will do no harm. Then it slowly feeds it out again, as the muscles use it up, always keeping the amount in the blood at two lumps. But if we eat or make more sugar than the liver can pack away, then the rest is changed into fat and stowed under the skin and around the muscles. So we store our food as fat, and use it as sugar—fat, luckily, being one of the few things we make in our bodies that are not poisons.
XXXIX
Snake Venoms and Others
The life of any creature, man, animal or plant, is one long fight against being poisoned. The poisons get us in all sorts of ways. Some, like strong acids and caustics, actually destroy the flesh, just as they would eat a hole thru the top of a stove, and we are crippled or die for lack of a lining to our stomachs. A great many poisons, like alcohol, ether, chloroform, the various alkaloids, such as strychnin and atropin and cocain, which we use as medicines, and nicotin, which is the alkaloid of tobacco, the poisons of many toadstools, caffein (don’t call it caf-een, but caf-fe-in, like co-ca-in) which we get in tea and coffee (and therefore ought not to drink either till we are quite grown up) and half a thousand others, mostly with names ending with “in” and the ptomains (again it’s three syllables, to-ma-in) which form in fish and ice-cream that have been kept too long, and poison whole families at once, all these do not do any special harm in the stomach. But when they get into the blood stream, they go straight for the nerves and upset them. Ether, chloroform, and cocain, as we all know, begin by paralysing the pain nerves. The pain sense is cut off from the brain, so that no matter how much damage is being done, we don’t know anything about it. And a mighty good thing it often is that we don’t!
Other poisons attack the blood. The fumes from burning charcoal and some sorts of gas that we use for lighting and cooking, lock the oxygen of the air so tightly to the red blood corpuscles that are carrying it to the cells, that the cells cannot get it away from them. So the tissues die from lack of air, tho there is plenty and to spare in the lungs and the blood—only the blood hangs onto it, and the rest of the body cannot pry it loose. Snake poisons, also, kill by attacking the blood, thus cutting off the supply of air. These dissolve the blood corpuscles that carry the oxygen, and literally “turn the blood to water.” Then the blood, having no corpuscles, cannot carry oxygen to the cells of the body, and the body dies of suffocation, tho the lungs take as much air as before. Snake venom, therefore, does not do the least harm in the mouth or stomach. One can suck the poison from the wound made by the snake’s teeth, and spit out the poisoned blood, or even swallow some of it, without the least danger. One could wash himself in rattlesnake poison, and take no harm, so long as he kept a whole skin so that nothing got into his blood.
Perhaps you know that pigs are the great enemies of rattlesnakes, killing them and eating them up as if the serpents were so many apple parings. The rattlesnakes bite the pigs. But the pig’s skin is thick, and under it is a great layer of fat, in which there is almost no blood. So when the pig gets a dose of poison under his skin, enough to kill two or three men, he does not mind it at all. The venom, shut up in the fat, works out into the blood so slowly that the pig can make new blood corpuscles almost as fast as the poison destroys the old ones. So at the worst, the pig feels only a little discomfort. But the rattlesnake is safely tucked away in the pig’s inside, where it will never do any more biting.
What I want you to remember, then, is this: All living things are poisonous. We, ourselves, are continually manufacturing in our bodies carbon dioxid, sugar, ammonia, and a score of other things, any of which would soon put an end to us if we did not have a special machinery for getting rid of them before they get a chance. A great many plants produce also certain special poisons, strychnin, nicotin, and the like, which would kill them if they made too much. A few animals, too, like the snakes and some fishes and various insects, manufacture poisons, which also would kill them. In general, the blood of any animal is a poison to an animal of any other sort, and always a poison of the same sort as snake venom which does no harm in the stomach, but is fatal when enough is taken into the blood. In general, then, each creature has some means of getting rid of its own poisons, but the poisons of any different sort of creature will kill it.
XL
Of Measles and Rusty Nails
Little boys sometimes get careless on Fourth of July. Perhaps they let a cracker go off in their fingers. Perhaps they pull off a toy pistol without noticing where it is aimed. Boys have been known to do both these things.
When this happens someone is pretty likely to get a hole blown in his skin. That of itself is not especially serious; the hole will soon close again. But we are pretty certain to be dirty on the Glorious Fourth, especially if we have been round the streets, in the dust that people’s feet are stirring up. So when we blow holes in our skin, we are pretty likely to blow dirt in also.
City dirt has a great many different things in it. Among them, almost always, certain very small plants, far too small to be seen except with a pretty strong microscope. These are, in fact, a particular kind of bacteria. So we blow thru our skins, hole, dust, and bacteria. The hole heals over, but the bacteria stay inside.
Being living plants, they grow in the blood—like mold in bread or yeast in dough. Being living things, as they live, they make poisons. It happens that this particular plant makes an especially deadly poison, which goes straight for the nerves. Then the victim has convulsions, and almost always dies within a few days.
This is, in fact, the dreaded tetanus or “lockjaw,” which used to kill scores of boys and girls every Fourth of July. Sometimes, too, one catches it by stepping on a rusty nail, not because the rust on the nail does any special harm, but because a rusty nail is likely to be a dirty nail also, with the tiny living plants mixed in the dirt. We rarely get lockjaw from an ordinary cut with a sharp knife, because such a wound bleeds freely and washes itself out. The dangerous wounds are small deep holes and ragged tears, that give the little living plants a chance to hide and grow.
All catching diseases are like Fourth of July lockjaw. Measles, whooping cough, chicken pox, ordinary colds, grip, and many most dreadful sicknesses of which people die, all such are caused by some living thing which gets into our bodies, grows there, and living and growing, poisons us with its waste products. Some of these plants grow in the lungs, like that which causes consumption. In some, like diphtheria, the growth is in the throat. In summer complaint, which sickens the babies in the hot weather, the trouble is in the bowels. Even some sorts of baldness are due to growing things at the roots of the hair. Mostly, however, the plants grow in the blood. In any case, the poisons they make get into the blood; and there they poison the nerves, like the various alkaloids I told you about, or else they attack the blood itself, as the snake venoms do.
Some of these disease-making things, too, are not plants but animals. Such, for example, is the minute creature that causes malaria; and another that makes the dreadful “sleeping sickness” that every year is killing thousands of wretched negroes in Africa, in spite of all that can be done to prevent it.
They get into our bodies in all sorts of ways. Some come in the dust, when we breathe dirty air. Some come in dirty water. Some, a great many, come in dirty food, on lettuce and celery that have been carelessly washed, and especially in dirty milk. Some of the worst of all among them, the germs of typhoid fever, are carried on the feet of the common house fly, and planted all over the things that we are going to eat. Rats and mice also carry diseases—in their fur, on their feet, or even in their blood. So, too, do certain stinging, biting, and sucking insects; and when they bite or sting or suck the blood of some larger creature, they plant the seed of some disease in his body, where it grows and flourishes until the animal sickens and perhaps dies. No one, for example, ever catches yellow fever or malaria unless he has been stung by a mosquito which has already bitten somebody else with the disease. The mosquito picks up some of these living germs in the blood of one person, and sows them in the blood of the next; just as one might take seed from one field or garden plot and sow it in another.
All the catching diseases, then, from ordinary colds to pneumonia, and from measles and chicken pox to typhoid and scarlet fevers, are nothing in the world but living plants or animals growing in our bodies and poisoning us. We say that we catch the disease. Really the disease catches us. The disease is a living thing, that in very real sense, hunts for us, and catches us as a lion or a bear might do, or a poisonous snake. If we could kill these lions, bears, poisonous serpents, bacteria, and the rest, why then they wouldn’t get a chance to kill us. Then we should all live to old age—unless we poisoned ourselves, as I am sure some persons are quite foolish enough to do, or met with some accident that we could not help. But of course there are a few other diseases, like rheumatism and heart disease and indigestion, where the trouble may be with ourselves and not with any other living creature that gets after us.
Just to show you how one of these living, catching diseases manages to get on, and when one victim dies, changes over to another, I am going to tell you about something that I am sure you have already heard of either in your history, or else in stories that you have read about the Middle Ages, when the knights wore armor and the yeoman fought with spears and bows.
In those good old times, every little while, whole cities would be smitten with a terrible disease called the plague. Perhaps you already know about the Great Plague of London in 1665, when seventy thousand people perished, and the dead lay in the streets because the living were too few to bury them. The same man who wrote the story of Robinson Crusoe, wrote also a story of this great plague, not a pleasant story, naturally, but one that you will want to read later when you are older.
The trouble was nothing in the world but dirt and rats. The rats lived in the dirt; and the minute, living plant that makes the plague, lived in the blood of the rats. From them it got into the blood of human beings. But so long as a city kept clean and free from rats, it never had the plague. But when it let itself get dirty, as ancient cities usually did, then it might lose a fifth of its inhabitants in a few months.
As people, therefore, began to be more decent, the plague began to disappear; and after about the time of our Revolutionary War, most of Europe had become so clean and civilized that they had no more plague there. But still it lingers in other parts of the world, where there is more dirt, and where people, instead of putting their waste tidily away in the bucket or burning it up, throw it out the back door for rats to eat. Always, even now, the plague threatens Asia. During the first ten years of this very civilized twentieth century five million persons died of it in India alone.
And all because of dirt and rats and fleas. The rat lives in the dirt. The fleas live on the rat, and when they bite the rat, get a stomachful of blood, and with it some five thousand or so of the little plants that cause the plague. Then the flea jumps off the rat, on to a man, and bites him. Then a few of these five thousand germs get into the man’s blood. By the next day, these few have become millions. Within a week, often within two days, the man is dead—simply poisoned. But if the man had kept his house clear of rats and his skin clear of fleas, by keeping them both clean, he would not have been poisoned at all.
I am sorry to say that since the year 1900, and even as late as 1909, there have been cases of the plague in one or two especially dirty cities in the United States. So the National Government had to interfere, to make them clean up and get rid of their rats. Otherwise we might have had a terrible time; while as it was, some three hundred people died—which is more human beings than most of us know by name.
But you can’t have the plague without rats, and you can’t have rats without dirt. So, therefore, every civilized government in the world keeps men at work in its seaports, killing the rats that come in the ships, lest they bring the plague from China or India, where they don’t mind a little dirt.
There is another animal, dirtier even than the rat, and on the whole rather more dangerous—and that is the fly. Wherever there is dirt, there are pretty sure to be the germs of various diseases. If there is anything the fly likes, it is dirt. He eats it; he wallows in it. The dirt sticks to his feet, and the disease germs stick to the dirt; for a fly is not nearly so much smaller than an elephant as a disease germ is smaller than a fly.
Then the fly tracks over our food or falls into our milk. He may carry a million germs on his body, and every time he puts down one of his six feet he plants at least one. In forty-eight hours this single one may have grown to sixteen thousand. Then some boy or girl eats the food and is sick; or some baby drinks the milk and dies.
XLI
The Great War
The hardest battle we have to fight is with these living diseases. They kill more people in each year than have perished at the hands of the enemy in all the wars we have ever fought. During our war with Spain, the flies alone killed in camp four times as many of our soldiers as the Spaniards killed in battle. Every day of our lives in war and in peace, we are fighting for our lives against these unseen foes of pestilence and disease.
This is how we carry on the campaign. Our first line of defense is keeping clean. Every city now-a-days has men who watch its water supply. The surroundings of its ponds and reservoirs are carefully guarded. If necessary, the water is filtered before it goes into the street pipes. Always, if the city is half civilized, it filters all its sewage before turning it into the rivers. Thus, if there are any living animals or plants in the water, they get strained out. In many houses, where the people are especially careful, they strain or filter the water once more, or boil it till they kill every living creature therein.
Then every city has other men to look after its milk. Because milk, being good food for us, is good food also for other living creatures; so that if one single germ gets into a bottle, it will shortly grow to many millions, and play sad havoc with the family that uses it. Careful people, too, do not depend on the city to keep their milk clean, but see for themselves where it comes from; especially if there are children, for children not only drink much milk, but are peculiarly liable to catch the diseases which come in it.
Careful people, in addition, look out that all their food is clean. They see that none has been kept out where dust may fall in it, where rats or mice may brush against it, or where flies may track over it. In all these ways, the seeds of diseases may get sown in our food. One ought to make sure that there are no rats, mice, or flies in the house at all; and one ought to make sure also that all raw foods, like lettuce and celery are thoroly washed, for these often carry the eggs of certain animals, living eggs which will hatch out inside anybody who swallows them, and not be at all to his advantage.
That, then, is our first line of defense—keeping our food clean, lest the enemy enter through our mouths. Our second defense is to keep the air we breathe, clean and fresh and dust free, lest the enemy attack us by way of our lungs, and we die of pneumonia or consumption, or sicken of common colds and the grip. In all this, we are like a country with a powerful navy which can prevent the enemy from making a landing on its coast. So long as we keep these minute foes out of our houses, and still more so long as we keep them out of our cities, they cannot get near enough to us to do us any harm.