The effects of crotalin on the elapsed time in causing platelet plug formation upon the irradiation of venules in mice. Fluorescein sodium (150 μg per mouse) was intravenously injected 10 minutes before the irradiation, and the irradiation was then started for inducing the formation of thrombus at the indicated time intervals after the IV administration of crotalin (300 μg/kg). Values are presented as mean ± SEM (n = 5-6). BL indicates baseline value. (▿) Represents the occlusion time of each mouse measured at the indicated time. *P < .05, **P< .01 as compared with basal value.