The Special Sleep That Kicks In During a Sickness

In 1909, the Japanese scientist Kuniomi Ishimori collected spinal fluid from sleep-deprived dogs and injected it into active, rested pooches. Within hours, the latter fell into a deep sleep. By coincidence, a pair of French researchers did the same experiments a few years later and got the same results. These studies, and others like them, suggested that the blood of sleepy animals contains some kind of soporific secret sauce of chemicals. Ishimori called these “hypogenic substances.” Others labeled them “somnogens.”

The sources of these sleep-inducing chemicals have proved surprisingly elusive, and scientists have found only a that fit the bill. Now from the University of Pennsylvania —a gene called that triggers sleep, at least in fruit flies. Unexpectedly, it becomes active during infections and acts to kill incoming microbes. It seems to be part of a self-regulating system, analogous enough to an internal thermostat that we might call it a sleep-o-stat. It can send animals to sleep when they most need shut-eye, whether because they’re sick or because they just haven’t slept enough.