“It is difficult for a man to understand something when his income depends on not understanding it.”——H.L. Mencken
Soluble fibrin is the “universal protein of tissue repair.” It is so ubiquitous as to be ignored. Thrombin converts fibrinogen to soluble fibrin that appears in pus, exudates, scabs, scars, saliva, mucus, and milk. It escapes the vascular system via inflammatory gaps in the vascular endothelium and infiltrates damaged tissues, where it creates a lattice of fibrils that promotes fibroblast proliferation and collagen production that enables the formation of granulation tissue that fills empty spaces as part of the tissue repair mechanism. Excessive insoluble fibrin causes tissue edema, organ dysfunction, fibrosis, and scar formation.