The enteric nervous system (ENS) is an autonomic "brain-in-the-gut" that integrates gastrointestinal motility, secretion and blood flow into homeostatic patterns of gut behavior . Experimental models for the ENS are the same as for all independent integrative nervous systems, whether in the vertebrate brain and spinal cord or in invertebrate animals. The ENS coordinates and organizes the behavior of the musculature, secretory glands and vascular system, in each of the specialized organs of the gastrointestinal tract, into meaningful behavior of each organ. The ENS stores a library of programs for differing patterns of small and large intestinal adaptive behaviors. Programs in the library are akin to 21 st century digital "apps" that run on smart phones, tablet computers and comparable devices.