I have, on multiple occasions now, given massive amounts of blood. I’ve also given saliva, stool, and urine samples—sometimes 24 hours’ worth. And then, when I go to Houston every few months, I get MRIs of my brain and heart, and ultrasounds of my cardiovascular system and optic nerve. They send the ultrasound machine right into the goo on your eye. For some tests they put me in a contraption—a lower-body negative-pressure device—and have me take nitroglycerin. I don’t even know what experiment it’s for.