The sense of smell depends upon tiny particles of things coming in the air to the lining of our noses, especially certain parts of the lining of the nose. When we have a cold, this lining, or mucous membrane, of the nose gets swollen, and produces a much greater amount of mucus than usual, as we all can tell by the number of handkerchiefs we have to use in a day.

The chief reason why we can not smell so well when we have a cold is probably that this mucous, constantly pouring out of the lining of the nose and running over it, prevents the scent of things from getting to the sensitive part of the nose, and washes away any solid scented particles. Also, it may be that the poisons produced by the microbes that cause a cold poison the living cells of the mucous membrane and also poison the tiny ends of the nerves of smell that run to it, so that, even if scented things do reach the sensitive part of the mucous membrane, they can not be felt.

This applies alike to scents coming in from outside and also to the scents of food, which pass up at the back of the roof of the mouth into the nose, and which, when we have not a cold, help to give our food half its flavor.

Perhaps you have seen a hay fever sufferer, in the summer, sneezing violently and showing every sign of a serious cold. Hay fever is not a cold. It is not caused by a germ, but by the pollen of some plant, carried by the wind against the over-sensitive membranes of eye, nose and throat of the sufferer. It comes usually to people who, besides having sensitive mucous membranes, are tired or nervous; and every attack makes the sufferer more liable to another. Several plants such as goldenrod, dandelion and ragweed are chief offenders in causing hay fever.

Various cures have been attempted. The best cure is removal to the mountains or to the seashore, far away from the pollen. Various drugs, including cocaine, have proved helpful; but the effect of these is only temporary. Sometimes relief is provided by cauterizing the sensitive area of the mucous membrane. Some doctors inoculate the patient in order to build up resistance to the disease. Another method of warding off hay fever is to wear a mask provided with a filter in all areas where pollen is apt to be carried about by the wind.

Hay fever belongs to the family of allergic diseases, in which a person becomes ill because of special sensitivity to a certain food or drug or heat or cold or pollen or dust or even sunlight. Here is a remarkable illustration of the old adage that “one man’s meat is another man’s poison.” In no case is this truer than in the case of allergy.

The dollar, the standard unit of money in the United States, Canada, Mexico and several other countries, has a most interesting history, and so has the $ generally used to represent it.

The word dollar comes from the Low German for Thaler, which is an abbreviation of Joachimsthaler. Joachimsthal (Joachim’s dale) is a little town in Bohemia near which, in the beginning of the sixteenth century, a rich silver mine was discovered. The feudal lords of the town had coins made which, because of their excellence, were soon used all over Europe. These and similar coins were called Joachimst haters, or simply Thalers.

Coins of similar value were issued in Spain. They were called pieces of eight, because their value was divided into eight smaller coins. All these coins circulated freely in the colonies in both North and South America. In North America they were called dollars.

When the United States had been formed, the word dollar was adopted definitely for its unit of coinage, but the sign for the new coin was that of the old Spanish piece of eight. This sign showed the figure 8 (which strongly resembles the letter S), crossed by two lines representing the Pillars of Hercules, the gateway between Mediterranean and Atlantic at the southernmost tip of Spain. Thus the dollar sign really has nothing to do with the letter S, nor was it, as some people believe, originally formed by placing a narrow U over an S to form the monogram of the United States.

Some of the cells of the hair contain a pigment (coloring mattef). As human bodies grow old, most of them lose the power to make new pigment, so that the hairs are colorless, or white. Some people lose the power to make the pigment when they are still quite young others do not grow gray until they have reached a very advanced age.

General health and good care of the hair may aid in keeping the color. However, loss of hair pigment runs in families, and many physicians believe that it is a hereditary trait. The condition of the nervous system has an effect upon the hair. Persons under a serious nervous strain have been known to grow gray quickly. We hear stories of people who turned white in a single night, because of shock, or fright or fear. Probably these stories are exaggerations; yet it is true that men and women under stress have become whitehaired in a few months.

Scientists have studied for years, trying to find out what happens in the body that stops production of the color cells. In some cases, the mysterious little vitamins play a part. If the body lacks certain vitamins of the B family, the hair may grow gray. When these vitamins are supplied, the hair may regain its color.

Many animals also grow gray with the years. You have noticed this, of course, among cats and dogs. It is true of mice and rats and they are often chosen by scientists for experimental specimens.

When people have had smallpox or measles or scarlet fever once, they seldom suffer from them again, even if there should be an epidemic all around them. In some way or other the tissues of the body have become changed as the result of the first attack, and are better able to resist that particular kind of infection. We say then that the body is immune to that disease. Doctors make use of this immunizing power of the body, in a very wonderful way. They can give us a very mild form of a disease, or of a similar disease, by vaccination, and after that we are safe for years from any danger of getting the disease itself. For example, vaccination protects us from smallpox. People are often vaccinated against typhoid and other illnesses; they are inoculated with the actual disease germs, which have been killed or weakened to the point where they are no longer dangerous. To inoculate simply means to introduce into the body disease germs or their products.

Sometimes, instead of actual disease germs, a person is inoculated with blood serum of an animal that has been given a disease and has created in its blood “antibodies” that fought and killed the disease bacteria, or anti-toxins that rendered harmless the poisons produced by the bacteria.

Diphtheria anti-toxin belongs to this class of medicine that prevents disease or, if given in the early stages, cures it.

Our muscles, as we call the bands of flesh which move the different parts of our bodies, can move only when directed to do so by our motor nerves, which may be roughly described as telegraph wires between our nerve centres and our muscles. Before the mysterious order is sent from the nerve centre along the motor nerve to the muscle directing it to move, the nerve centre has to receive a message from another and quite different nerve called the sensory nerve. Scientific men call this reflex action.

From the brain, or from the spinal cord (the big nerve which runs up the backbone) motor and sensory nerves are connected to every part of the body. If a motor nerve is cut, we lose all control of the part of the body it serves, but sensation remains. If a sensory nerve is cut, we lose sensation in the part which it serves, but retain the power of movement. If both are cut, we lose both sensation and the power to move.

Fortunately, serious damage to a nerve does not often occur, but we sometimes experience what undue pressure on a nerve can do. If we sit on a chair so that a sharp edge presses the nerves of our leg, we may easily find that our foot ‘goes to sleep.” What has happened is that pressure has affected the nerves serving the foot, and by compressing their fibres has made them incapable of transmitting impulses. On attempting to rise we can not feel our foot because the sensory nerve has been pressed, and we can not direct the foot to act because the motor nerve has been pressed. The foot is numb. Gradually the nerves recover as the pressure is removed, and we get the tingling we call “pins and needles.”

In order to understand this we must realize that we do not sleep in just the same way all through the night. At first we sleep deeply. Now, it is good to sleep deeply. It makes us look well and beautiful, and people seem to have noticed this, for they call the first hours of sleep the “beauty sleep.”

But for some hours after this we sleep less and less deeply. We can easily find this out by noticing exactly how loud a noise is required to wake one up at various times in his sleep. And we find that when a person has had nearly enough sleep he will be wakened by a noise which, a few hours before he would not have noticed.

That is the sort of thing that happens when we wake. We have been sleeping less and less deeply for some time, and our brain has almost awakened of itself. Then there comes a sound or a light, or perhaps we move in bed and feel ourselves moving, and since we are already very nearly awake, the sound or the light or the feeling wakes us up. Of course if we lived out-of-doors, as men did long ago, and as birds do still, light would wake us up. That is what wakes the birds now.