Someday, if a cancer succeeds, it will produce a far more perfect being than its host.Preparatory to the observation, Mukerjee has noted that an emerging, although highly controversial, answer to the question of what allows a cancer cell to keep dividing endlessly without exhaustion or depletion generation upon generation is that cancer’s immortality is actually borrowed from normal physiology and, specifically, the stupendous fecundity of stem cells. No less remarkable (at least to me as a naive and ignorant reader) is the ability of the body as a whole to switch this on and off:
The human embryo and many of our adult organs possess a tiny population of stem cells that are capable of immortal regeneration. Stem cells are the body’s reservoir renewal. The entirety of human blood, for instance, can arise from a single, highly potent blood-forming cell (called a hematopoietic stem cell), which typically lives buried inside the bone marrow. Under normal conditions, only a fraction of these blood-forming stem cells are active; the rest are deeply quiescent -- asleep. But if blood is suddenly depleted, by injury or chemotherapy, say, then the stem cells awaken and begin to divide with awe-inspiring fecundity, generating thousands upon thousands of blood cells. In weeks, a single hematopoietic stem cell can replenish the entire human organism with new blood -- and then, through yet unknown mechanisms, lull itself back to sleep. I also read Will Self's essay on blood disease and drug addiction. Death, writes Self, remains the most metaphoricised phenomenon of all. Cancer, though, is also a distorted simulacrum of life.
 Even in normal circumstances, however, haematopoiesis reportedly manufactures more than 100 billion new blood cells every day