The first phase of healing is the lag period. This is the time when the wound is being cleared of necrotic tissue and contaminants. The strength of a wound is maintained only by a fibrin clot between the edges and any supplemental strength the surgeon may give to it, such as with sutures. The first reaction is a dilatation of the capillaries and of the accompanying arterioles. Accompanying this dilatation is an increase in capillary permeability. As a result of these reactions, plasma proteins, as well as other constituents of blood, may readily escape into the wound. The fluid can coagulate and form fibrin, which has the effect of sealing the wound and stopping the bleeding. This fibrin network will also form the scaffolding for further events. Bleeding of the disrupted capillaries is partially stopped in this manner. The major bleeding is controlled by the clotting mechanisms of the blood.