Abstract
The development of the intramural plexuses in the tortoise, Geoclemys reevesii was inferior to that observed in the fowl: the meshes of both Auerbach's and Meissner's plexuses were coarser, and consisted of less number of nerve fibers. Occasionally, a small ganglion was seen at the crossing points of the meshes. The average number of nerve cells contained in the ganglion was estimated to be 1500/cm2, being about half as much as that estimated in the fowl.
When the mucosa of a colon in vitro was stimulated mechanically by stroking or chemically with 1/10 N HCl, the excitability of the colonic muscle was raised at the region oral to the stimulated spot, but lowered at the region anal to it. These effects were abolished by applying a ganglion-blocking agent, hexamethonium (10-6 g/ml), to the mucosa.
When the intraluminal pressure of a colon in vitro was raised from 0 to 3-12 cm H2O, the colon was distended at first but soon contracted powerfully. The contraction became extremely reduced or was abolished when hexamethonium (3.5×10-7-1×10-5 g/ml) was added to the saline solution in which the colon was immersed.
The results indicate that the intramural ganglion cells serve as the center of the intrinsic mucosal reflex.
