[One possible mode of protective actions of mucin in the digestive canal]

This report describes an additional fact indicating the protective action of mucopolysaccharide in the digestive canal. Roughly speaking, the living organism is composed of structural and functional (physiologically active) substances. Through experimental observations, we have now got the theoretical idea that a functional substance not only possesses a proper inherent activity but has acquired new accessory activities during developmental course. For example, as shown in the previous papers, the authors have revealed that mucin, which is originally an intensive lubricant to make or to transfer the bolus, can be an agent to initiate, maintain or promote the spontaneous movement of the isolated intestinal strip. In this paper, when acetylcholine is applied to the bathing solution of the strip together with eserine, its promotive effect on the spontaneous movement is abolished by mucin probably because of direct binding which renders acetylcholine ineffective.