It was a warm summer morning. The last of the ocean fog had burned away, and the air was still. In an old car held together by paint and duct tape, an outcast drove slowly down the street - looking for the address he had been given when he phoned the day before. Soon he spotted it, and then found an open parking space about a block away.
He was early for his appointment, so he waited in the parked car for a little while. Then he walked back to the building he had just driven past and went inside. The front office was empty, so he sat down and waited. After a couple minutes, a receptionist entered the room and asked him his name and appointment time. She wrote something down on a piece of paper, and then told him he could go on back to the room down the hall.
So he walked back to the small lab a few feet away. There was a nurse inside waiting for him. She scowled when she saw him, and sounded mad enough to spit as she asked a few questions preliminary to the drawing of blood. After he handed her the paper that he brought with him, her demeanor quickly changed. "Oh," she said, "you're in the control group?" Her face brightened and she almost smiled. The harshness left her voice as she asked him to roll up his sleeve.
As the blood filled up the syringe attached to his arm, he began to look around the room. On a low shelf there were dozens of glass tubes filled with blood. They had colored labels on them. The light-colored labels said "schizophrenic", and the darker ones said "control."
Finally the last tube was filled, and she removed the needle from his arm. She put a bandage over the needle mark and then handed him a sheet of paper to take to the receptionist. He went to the front and got his pay, and then left; as glad to be out of that place as he was to finally have a little bit of money.
The small facility had no equipment of its own to do complicated tests on the blood that was collected there. Instead, it was all mailed to a large laboratory in another city, and there broken down into various component parts, which were measured and analyzed in many different ways.
At great expense, any and every kind of difference that could be found between the two different groups of blood was recorded and then published in an article in a respected medical journal. The article commented extensively on what substances tended to be present in greater or lesser quantities in the blood of one classification of people versus that of the other classification.
All the authors of the study were congratulated by their colleagues and peers, and their reputations were significantly enhanced. Before the collection phase of the study was over, the nurse who extracted blood from every study participant learned to always check each one's paperwork before deciding how to treat them.