Are you a morning "lark" or a "night owl"? Do you put your feet up after lunch, or can you get by on a few hours' sleep? Foster, a professor of molecular neuroscience in London, and Kreitzman (The 24 Hour Society
) survey the biological clocks that dictate circadian rhythms, the daily cycles that affect creatures from cockroaches to humans. A little bundle of nerve cells in the front of the brain called the suprachiasmatic nuclei is responsible for many circadian functions in mammals. Other controls may be embedded in our genes. The authors explain that all living creatures run on several different biological clocks simultaneously: some make it possible for us to recognize the passage of short intervals of time, whereas others (in the retina) respond to light and regulate our bodily functions over 24 hours and even longer cycles. Your very perception of time depends on your body temperature, which varies by almost one degree Celsius during the course of a day. In their final chapters, the authors explain that the very efficacy of medication for many diseases, notably cancer, depends on when it is administered. Biology buffs will marvel at the fascinating material, and medical professionals should put the book at the top of their must-read lists. (Sept.)
