“Usually the result is a spherical ball of cells,” said Nicolas Chevalier, a biophysics researcher at Paris Diderot University. “It does not have the classical, elongated, cylindrical shape.”

Researchers already knew that, very early in an embryo’s growth, the muscle surrounding the gut starts to pulse rhythmically, eventually becoming the peristaltic motion that moves food from the stomach to the colon. Dr. Chevalier and his colleagues were curious to see what encouraging this motion in lab-grown gut would do. So they designed a series of experiments using chicken embryos, a common model organism in the study of embryonic development.

Early on in developing chickens, as in humans, the gut stages an impressive jailbreak from the rest of the embryo. Through a large hole, it pours out and settles down for a period of growth outside the body, before eventually being drawn back in. The scientists studied these extruded guts, which were no more than about an inch long, from chicken embryos.

First, Dr. Chevalier attached small weights to one end of some guts and grew them vertically, alongside others without weights, to see what applying gentle force would do over time.