On cancer vs. tuberculosis:The cancer cell is a desparate individualist, "in every possible sense, a nonconformist," as the surgeon-writer Sherwin Nuland wrote. The word metastatis, used to describe the migration of cancer from one site to another, is a curious mix of meta and stasis - "beyond stillness" in Latin - an unmoored, partially unstable state that captures the peculiar instability of modernity. If consumption once killed its victims by pathological evisceration (the tuberculosis bacillus gradually hollows out the lung), then cancer asphyxiates us by filling bodies with too many cells; it is consumption in its alternate meaning - the pathology of excess. Cancer is an expansionist disease; it invades through tissues, sets up colonies in hostile landscapes, seeking "sanctuary" in one organ and then immigrating to another. It lives desparately, inventively, fiercely, territorially, cannily, and defensively - at times, as if teaching us how to survive. To confront cancer is to encounter a parallel species, one perhaps more adapted to survival than even we are.