Tail bleeding models. Blood was collected after 2-mm (A) and 4-mm (B) tail transections for 30 minutes (A) and 10 minutes (B) in a fresh tube of saline; total blood loss (in microliters) was then measured. F8^+/−Pros1^+/+ (white columns) and F8^+/+Pros1^+/+ (green columns) mice served as controls (n = 5 for all groups in panel A; n = 6 for all groups in panel A). (C) An anti-human PS antibody altered tail bleeding after a 4-mm transection. *P < .05, **P < .01, ***P < .001, ****P < .0001; n.s., not significant.