The Chain Reaction of the Blood Clotting Mechanism in Relation to the Theory of Hemostasis and Thrombosis

THE PHYSIOLOGIC REQUIREMENT I F OCCASION arose to invent a blood clotting mechanism, it might be arranged for the blood to remain fluid in the vessels, yet promptly congeal when mixed with the juice of freshly cut tissue. This would probably work well for small punctures. However, as this mechanism was tested with larger cuts, an unexpected difficulty might appear. As the blood flowed through the break, a coagulated film would be deposited on the cut surface. This layer would seal over the wounded tissue and hinder the admixture of tissue juice with that portion of blood not yet clotted. Therefore, hemorrhage would continue through a passageway lined by freshly clotted blood. To overcome this difficulty a chain reaction might be introduced. Then, as one layer of blood was clotting, it would incite the neighboring layer to clot. Thereby the coagulation process could be propagated from one layer to the next, and tissue juice would be needed only to exert its effect on the initial layer. The mechanism could then achieve a hemostatic plug which would grow by accretion, and which, in this respect, would resemble the natural plug depicted by Tocantins.t Thus, by teleologic conjecture, we have arrived at some function a chain reaction might serve. Other functions can be imagined. Ordinary chemical reactions, be they stoichiometric combinations or enzymatic, begin rapidly and thereafter slow down. But, when a chain reaction is involved, one of the products accelerates the reaction, with the result that as more product is formed the reaction goes increasingly faster.* Hence, chain reactions may start with a lag period, but later are apt to proceed explosively. This offers opportunity for control during the lag period, but ensures rapid action when the lag has been passed or overcome.