Hydrochloric AcidStomachPneumonia, AspirationNitric AcidGastric JuiceDecalcification TechniqueTrifluoroacetic AcidCountercurrent DistributionEsophagusGastric MucosaHydrogen-Ion ConcentrationStomach NeoplasmsGastric AcidParietal Cells, GastricAcidsAchlorhydriaFluoroacetatesStomach UlcerGastric FistulaSulfuric AcidsPentagastrinDuodenumPepsin ASodium HydroxideAlkalosisAppendixAcidosisStomach DiseasesSodium ChlorideSecretinBicarbonatesSpectrophotometry, AtomicGastrinsGastroesophageal Reflux