Ang Dugo....Bow!

They only discovered that blood came in different types in 1900. The National Blood Service was set up 46 years later to collect and provide blood supplies for all the hospitals in England and North Wales. 8,000 units of blood are needed every day to meet this demand, which keeps rising.

Blood comes in four main types - O, A, B and AB. Group O is the most common which means it's in demand the most. But blood can also be subdivided into its main components - red cells, white cells, platelets and plasma. Unfortunately red cells only last 35 days and platelets are only good for five days.

Want to know what the top 10 uses of blood are?

1: Straight in is General Surgery with a whopping 23%.

2: We have General Medical with 15%.

3: Cardiothoracic (that's heart and chest surgery to you and me) with 13%.

4: A figure of 11% puts Orthopaedics here - that's anything to do with bones and bone diseases.

5: Haematology (blood diseases) with 9%.

6: Accident & Emergency (what you see on "Casualty" every week) with 8%.

7: Renal or anything to do with the kidneys with 6%, along with

8. Neonatal & Paediatrics, which is the treatment of newborns and children.

9: Intensive Care with 4%.

10: Obstetrics & Gynaecology (anything to do with pregnancy and childbirth) weighing in with 3.5%

It's a given fact that people in different countries are, well, different. Languages, attitudes, eating habits, that sort of thing. Well, the same holds for their blood groups and distribution too.

Almost all South American Indians are group O, while about 25% of Asians are group B. Only about 9% of Caucasians have that particular group. And should you find yourself in Norway requiring a blood transfusion, let's hope it's group A you need, because that's what they've got the most of up in that part of the world.

Blood groups have other uses too. Anthropologists can do their stuff, tracking the movement of ancient peoples and tribes by studying the difference in blood groups. For example, they've discovered that gypsies have a very similar blood distribution to the natives of North West India. Linguists already think the two were connected. The blood evidence confirms it.

The best place to find group O is in the north of England - a throwback to before the 8th century when everyone was that group, and before the Vikings came and messed up our gene pool.

But the South of England has a greater preponderance of group A. That'll be all those European invasions over the centuries. And if you're looking for group B, then look no further than among the Asian or Chinese communities. Almost anyone between the ages of 17 and 60 can become a new blood donor.

And those regular donors who are still in good health can still show up and donate for right up to the age of 70.

You've got about 5 billion red blood cells in every litre of blood (that's 5 followed by 9 zeroes, so all in all, it's quite a lot). Which means you have on average 25 billion red cells running around inside you, although 25 million (or 0.1%) of them die every day. That works out at roughly 300 a second, so it's quite unlikely you're going to run out of them.

William Harvey was the first physician to discover that blood circulates round the body back in 1628.. The first successful blood transfusion was carried out in 1665 by Dr Richard Lower, using animals as subjects. When they started performing transfusions on humans, initially with animal blood, they couldn't understand why their recipients kept dying. It wasn't until 1900 when Dr Karl Landsteiner of Vienna discovered that blood comes in four different groups. He got the Nobel Prize for his discovery. Didn't stop him dying of a blood clot though.