Experiments on Plasma Clot Contraction

1. Clot contraction was found to be associated with the action of whole, adhesive platelets. It was proportional to the number of adhesive platelets and not to the total number of platelets. It was inversely proportional to the fibrinogen concentration and a direct relationship was shown between the fibrinogen concentration and the number of platelets necessary to promote any fixed level of clot contraction.

2. Clot contraction could not be promoted solely by proteolytic agents and no association could be traced between clot contraction and proteolysis.

3. These findings are discussed with reference to the views concerning the mechanism of clot contraction.