The first heart transplant operation was carried out by Professor Christian Barnard in Cape Town, South Africa, in 1967. Sadly, the patient died after just eight days.

Humans blink once or twice every 10 seconds. Each blink lasts for one third of a second. This means that during every 12-hour day, you will blink for a total of about 25 minutes. New-born babies do not blink at all - they begin when they are about six months old. 

A fruit which grows in West Africa is known as 'miracle fruit' because it makes sour foods taste sweet. It is thought that it contains a protein which stimulates the taste buds to report the presence of sweetness when confronted with acids. 

The tastes of salt and sweet are closer than you might think. A very high concentration of salt (known as a threshold concentration) tastes sweet. 

It has been estimated that we need 25,000 times as much of a substance in our mouth too taste it as we do in our nose to smell it. 

Adults have about 9000 taste buds, and children have more than adults do. 

Substances which give off gas easily usually have strong smells - petrol, for example - because high concentrations of chemicals reach our nose from them. 

When we want to get as much of a smell as possible, we automatically sniff to increase the amount of air reaching our nose. 

If you cut or scratch the epidermis, the skin replace itself without leaving a scar. But damage to the dermis will cause a scar when the skin heals. 

The epidermis makes Vitamin D when the skin is exposed to sunlight. 

Excess salts and other substances are removed from the body by sweating. 

The mature sperm is much too small to be visible, but the development of the electron microscopes has made it possible to study minute cells. They have shown the whole sperm is about six hundreths of a millimeter long (55-65 microns, each of which is one thousandth of a millimeter). The head of the sperm is about five thousandths of a millimeter (5 microns from end to end). 

Chips contain three times as many calories as boiled potatoes. An unpeeled potato is better for you because it has almost twice as much fiber as a peeled one. Dried fruits are the richest source of natural sugar. 

In the West, the average daily diet contains 1 teaspoon of refined sugar per hour. It is present in most processed meats, sausages, tinned vegetables, soups and breakfast cereals. 

All body movements, from the twitch of an eyebrow to a high jump, are made possible by muscles. We even depend on them for digesting our food and for making our blood go round our bodies. 

People with diseases of the bone marrow can be given transplants. First, their own bone marrow is destroyed by drugs or radiation. Marrow drawn fron the pelvis or sternum of a healthy donor is then transferred into the patient's veins. 

Some people can bend their limbs in unusual directions and are often described as being double-jointed. They do not have two joints, but they can bend in strange ways because their joints are particularly flexible. 

The bones in your face protect the delicate sensory organs of the head, such as your eyes and tongue. They also provide a stable frame for your facial muscles, so that you are able to chew, speak or show emotion. 

Down's syndrome is the result of a genetic cell abnormality. The disease is incurable, but with care and attention, children with Down's syndrome can realize their full potential. 

We cry when we are upset, but no one really knows why. We blow our nose when we cry because tear fluid escapes down tiny holes in the inner part of the eyelids into the nose. 

Eating carrots really does help you see in the dark. This is because the vitamin A in carrots helps the rods in the retina to work effectively. Cabbage and other green leafy vegetables are also good for fighting eye disease. 

The human eye can see up to 10 million different shades of color. Human beings, however, cannot see ultraviolet light, unlike insects. 

Hormones are what make you unique. They dictate your physical and mental make-up: whether you will be tall or short, or fat or thin. 

Although belching is socially unacceptable in many cultures, it plays a useful role in the digestive process. Gas forms in your stomach from air swallowed with food or drink and builds up in the upper part until the cardiac sphincter allows it to escape into your esophagus. From there it is expelled from your mouth by an active muscular contraction, resulting in the familiar burp. 

Humans can survive for more than a month without food, but only a few days without water. Almost three quarters of the weight of a newborn baby is water. This percentage gradually drops as a person ages, which is why elderly people have wrinkled skin. 

One of the body's fat deposits is around the eyes. The fat is used by the body during illness or starvation, which is why excessively thin people have a gaunt expression.