The Body

It is divided into two hemispheres, each of which is principally concerned with one side of the body, but for reasons unknown the wiring is crossed, so that the right side of the cerebrum controls the left side of the body and vice versa. The two hemispheres are connected by a band of fibers called the corpus callosum (meaning “tough material” or literally “calloused body” in Latin). The brain is wrinkled by deep fissures known as sulci and ridges called gyri, which give it more surface area. The exact pattern of grooves and ridges in brains is distinctive to each individual—as distinctive as your fingerprints—but whether it has anything to do with your intelligence or temperament or anything else that defines you is unknown.

E. coli can reproduce seventy-two times in a day, which means that in three days they can rack up as many new generations as we have managed in the whole of human history.

Curiously, we don’t have any receptors for wetness. We have only thermal sensors to guide us, which is why when you sit down on a wet spot, you can’t generally tell whether it really is wet or just cold.