Thrombus formation and embolization in the carotid arteries of fbg^–/– mice produce large emboli that occlude large blood vessels in the brain. Immunostaining of brain sections from animals at the end of the experiments with polyclonal antibody to mouse platelets revealed large emboli occluding vessels in brains of fbg^–/– animals when compared to the control fbg^+/– animal or 7E9-treated animal (original magnification × 20).