Blood cells are not organisms!

I can't believe it. I just read a discussion wherein somebody claimed that blood cells are living organisms. (He was a staunch pro-choicer who said, "So what if the embryo is a living organism? So are blood cells!")

Now I don't want to discuss the abortion issue, so my point is not to take sides in that discussion. I just want to say that I was absolutely astonished that he said such a thing. You don't need to know about lymphocytes, leukocytes, antigen-presenting cells or any of those other technical details to know that blood cells are not organisms. They are alive, yes, but not in the same sense that a distinct living organism is alive.