The process of blood clotting resembles the first aid performed by ambulance crews called out to attend a traffic accident.
When bleeding takes place in any region of the body, blood platelets known as thrombocytes are dispersed throughout the bloodstream. Wherever bleeding may occur, thrombocytes will always be on call nearby.
Just like a traffic officer, a protein known as Von Willebrand indicates the site of the accident, halts the thrombocytes when it detects them and causes them to remain in the site of the incident. The first thrombocyte to arrive attracts others to the site by emitting a special substance, just as if it were summoning assistance.
At this point, 20 enzymes in the body come together to begin producing a protein known as thrombin, which is produced only in the presence of an open wound. This is similar to a first-aid team administering the necessary drugs at a crash site. In addition, the production must be at just the right level, and the production of thrombin must also start and stop right on time. The enzymes that produce this protein seem to decide among themselves when production should begin and cease.
Once a sufficient quantity of thrombin has been manufactured, small fibers known as fibrinogen form, creating a microscopic network in the blood, to which the thrombocytes adhere and accumulate. Once this accumulation has become sufficiently dense, bleeding stops These enzymes and proteins are structures consisting of different arrangements of blind, unconscious, inanimate atoms. Yet each one assumes a function from the moment the incident occurs and they are all "organized" in such a way as to halt the flow of blood in the most speedy manner. The apparent consciousness displayed by these collections of atoms is doubtless a great miracle and cannot, of course, be the product of "evolution," a process totally dependent on chance.
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