The enteric nervous system was defined originally by Langley early this century as a separate and autonomous division of the autonomic nervous system (Chap. 17) [9]. Not only was he impressed by its size (2 × 108 neurons compared with a few hundred fibers in the vagus nerve), but he also recognized its ability to maintain organized propulsive activity in intestinal segments studied in vitro. He, therefore, suggested that this intrinsic (enteric) nervous system was capable of integrative functions independent of any central nervous system influence. For several decades this concept was overlooked, and many textbooks described the enteric nervous system as a collection of parasympathetic terminal ganglia acting merely as relays for the parasympathetic preganglionic fibers (Fig. 70.1 A). This simple model ascribed no integrative functions to the enteric nerves and ignored the complexity of interconnections between enteric ganglia. The inference was that all neural control could be attributed to autonomic regulatory centers within the central nervous system and spinal cord.