The structure of clots made from reconstituted human whole blood activated with kaolin and mouse whole blood. (A-C) Scanning electron micrographs of clots made from reconstituted human whole blood consisting of 2 mg/mL fibrinogen, 167 000 platelets/μL, 37% hematocrit, activated by kaolin following recalcification. (A-B) Inside of these contracted clots, revealing close-packed polyhedra. (C) Outside of contracted clot, showing a thick meshwork of fibrin and platelet aggregates. (D) Scanning electron micrograph of the inside of a mouse whole-blood clot. Magnification bar = 20 µm (A) and 10 µm (B-D).