Bleeding times generated fromSyk^−/−, Syk^+/−, andSyk^+/+ mice. Radiation chimera mice repopulated with either (▴) Syk^−/−, (○)Syk^+/−, or (•) Syk^+/+fetal liver cells were anesthetized and 6 minutes later had 0.5 cm from the tip of the tail removed with a scalpel blade. Blood was gently blotted onto surgical blotting paper every 30 seconds until cessation of bleeding. The mean and standard deviations obtained for the bleeding times were 5.6 ± 3.4 (forSyk^−/−, where n = 5), 5.9 ± 3.1 (forSyk^+/−, where n = 7), and 9.8 ± 8.2 (forSyk^+/+, where n = 3).