If people lived to age 32, I would have had my educational mid-life crisis last year while I was sitting in AP Biology class. For my whole life, I had an aspiration to be a doctor and had enrolled in this class seeing it as something of a stepping-stone to my goal. But then it fell apart. I remember the moment clearly. Our teacher had my undeserving rapt attention as she droned on about the partial diffusion of sodium chloride through the Loop of Henle in the nephron, the operational unit of the kidney. As I looked down at what few items I had scribbled on my paper (a heading for my notes, the notes themselves, replete with sufficient question marks, and a scribbling of what could have been a large dog, or a banana), it occurred to me that I really didn't