Bob Holden, age 10, of Canoga Park, Calif
How many red blood corpuscles do we have?
In the past, certain hoity‑toity people were said to have blue blood. If you trace a blood vessel in your arm or leg it, too, seems to be carrying blue or purplish blood. But this is because you are seeing it through layers of skin, flesh and other body tissues. Crabs have blue blood, but all humans have red blood and nowadays it is a compliment to be called a red‑blooded fella. It means that you are strong, healthy and vigorous and you most certainly ate up your spinach, green vegetables and other blood‑building foods.
A glistening drop of blood is redder than the reddest rose. Its color comes from tiny cells, floating busily along in a stream of pale, clear liquid. They are called the red blood cells or the red blood corpuscles. Their job is to carry oxygen from the lungs to the various tissues throughout the body. Where the air is thin and oxygen scarce, it takes more red corpuscles to do the same work. For this reason, a person living in the mountains, say two miles high, may have twice as many red cells in his blood as a person living at sea level,
No one ever has counted the red blood cells in a human body one by one. Whatts more, some people have a little more blood and some a little less than others. We also must allow for altitude, whether the person lives high in the hills or low in the valley. The differing factors mean that we can take only an average count. We can make an estimate, an educated guess, and give a fairly accurate idea of how many red blood cells should be in the body of an average man.
The number is so big that a few million more or less makes no difference. Next time you get a scratch, stare very hard at the blood and try to see the tiny, floating red cells.
You can stare from now until Doomsday but you will never spot a single one of them ‑ for they are much, much too small for our eyes to see.
They show themselves only when magnified under a microscope and you have about 300 million of them .in every drop of your blood:
A grown man, weighing around 150 pounds, is likely to have 12 pounds, or about five and a half quarts, of blood. We can estimate that every drop in those five and a half quarts contains about 300 million floating red cells. A cubic inch of average blood contains about 75 billion red cells. In the entire blood stream of an average‑sized man there are roughly 30 trillion red blood corpuscles ‑ which in round figures is 30, followed by 12 zeroes. A young man of ten has a few million less than this.
All healthy red cells look alike and even an expert could hardly tell one from another. But some of them are youngsters and some are old fellows. Every day, one red cell out of every ten is scrapped and a new one takes its place. For the blood is always renewing itself and a red cell wears itself out after 127 days and nights of useful work.