Over the many years that I worked as a doctor in a major New York City hospital, I noticed a peculiar phenomenon occurring with my patients. Most of the vast number of ill or injured people who passed into and out of my care melted into one long blur as those years rolled by, while certain individuals continued to live in my memory as clearly as on the day I first met them. Only now, as I approach the end of my career, do I understand why this has been so. The reason does not involve personal preferences, nor does it reflect the degree of challenge that different patients presented, or any other such variable that would naturally set some apart from others. It involves another dynamic entirely, which I believe is this: those patients who remain alive in my memory are the ones who mark the measure of my doctor's heart. Katherine, Lily, and Nestor are three who do this for me, and their stories make clear what I mean. I came to know Katherine when I was a still-wet-behindthe-ears third-year medical student doing my monthlong clinical rotation in Internal Medicine, and she won me to her cause immediately. A slender, probably once-attractive, auburn-skinned woman in her late thirties, Katherine lay confined to bed in Room 301A on the medical ward with the most disturbing disease I had ever seen. Her diagnosis was faradvanced scleroderma, a condition in which a person's immune system becomes confused. Instead of producing antibodies that defend against outside invaders, it produces antibodies that attack the person's own connective tissues, those strong and marvelously flexible tissues that give our skin its suppleness and that form the bulwark of our muscles, our blood vessels, and all our internal organs. The attacking antibodies rob these connective tissues of their marvelous elasticity, making them grow stiff and hard and resistant to movement. Unfortunately, modern medicine has not yet learned how to stop this grim process. Once started, the disease can progress slowly or more rapidly, affecting its victim in merely a few places, or spreading through the person's entire body, as it was doing in Katherine's case. Katherine had begun to develop the early signs of scleroderma a decade earlier. A feeling of tightness in her skin, together with a shiny appearance, began first on her fingers and toes, and then also appeared on her elbows and knees. She had seen other patients whose condition was more advanced than hers in her specialist's office, and she knew what was coming. As time went on, the disease progressed, steadily gaining ground with its leathery unyieldingness, eventually closing in so fully all around her that she could do nothing but lie stiff and motionless in bed. She was encased in a body that would one day become her coffin.