Borders have always been unsettling to me. Such boundaries are places of unrest, displacement, and challenge, but these characteristics have within them seeds of constructivity and growth as well. Finding myself unexpectedly free for a day in Minnesota during the 33rd annual meeting of the National Association of Medical Examiners, I decided to take a long drive, traveling North all night to Duluth and then along the northern shore of Lake Superior along Highway 61. My destination was the boundary waters dividing the US and Canada at Grand Portage, Minnesota. As I approached the Canadian customs building, my heart began to pound in the fashion it always does at border crossings, my mouth dry and my voice almost but not quite shaking. I have crossed this frontier, the longest undefended border in the world, many times. I have never broken any laws, and I've always passed through quickly and uneventfully, but my autonomic reaction is always the same.

Within minutes, I was hiking alone along the Canadian side of the Pigeon River, looking across 30 meters or so of river water to the United States, reflecting on the sense of discovery and adventure that seem to accompany crossing those artificial, man-made lines, be they state, provincial, or international.

Could it be that borders are metaphors for the daily hinterlands in which we find ourselves, regardless of how near we might be to a political boundary? Trekking along the slow-flowing river toward an upstream waterfall, I was struck by the number and quality of borders I and others straddle all our lives.

In medicine, I am a forensic pathologist, occupying the porous border between basic and clinical science, flitting between the two like the birds above the Pigeon River, belonging to neither country but to both, until both the boundary between the two countries and the two branches of science seem almost arbitrary. As is true of many who dwell in border areas, I speak a mishmash of languages, of jargon and plain English, as I explain medical and autopsy findings to other medical personnel, bereaved families, police, attorneys, media, jurors, and others.

In my family background, true of so many Americans, I am the product of many borders crossed: my mother's parents Italian and Belgian Catholics, my father's Russian Jews. In my extended family's spiritual lives, we have had to choose upon what side of that border we will stand, my older siblings choosing that of their maternal side, I that of my paternal.

Other universal borders offering a daily struggle yet also an opportunity for learning: the often frustrating boundary between work and home, once more sharply defined, now in some instances fragmented to the point of nonexistence, with cell phones, pagers, and other "conveniences" which turn out to be anything but.

The borders of maturing and aging: as these lines are written, one of my children is on the cusp of adolescence and adulthood, his reticence a boundary across from his father's inherent talkativeness. Another child is emerging from childhood into adolescence, yet another not far behind. All this is occurring at the same time that one of my parents struggles with cancer, poised at the boundary of a long, productive life and a future that we cannot know.

Such were my thoughts as I crossed the border back into the United States and began to hike along the American side of the river, my quiet solitude occasionally punctured by an international squirrel or cosmopolitan songbird. In life as a whole, as is true of medicine in particular, we all must wrestle with and learn from the borderlands, those areas which test us and make us anxious yet ultimately allow us to grow. Perhaps it is not so bad that as we mature, we learn to straddle the border, seeing shades of gray where once we only knew black and white.