Summary

The mosr important thing for an organism's survival is "the maintenance of a constant internal environment" (149). This internal constancy is called homeostasis and it is accomplished "by the development of special nerve cells and nerve nets [...] as well as by direct chemical means (hormones, for example)" (149). When the bodies internal systems "are working harmoniously together, one feels 'well' or 'normal'" (151). Sacks refers to the work of Antonio Damasio who speaks of a "core consciousness" to describe "the basic feeling of how one is, which eventually becomes a dim, implicit feeling on consciousness" (151).

To illustrate this, Sacks discusses his work with patients who were suffering migraines; many of whom identified the onset of a migraine by a general feeling of "something amiss" (152). This "general feeling of disorder" continues and increases as the migraine gets more and more severe (153). Sacks attributes this...