By the term pyrosis is designated the ejection of chyme from the stomach into the oesophagus. As a rule, a burning sensation is then felt at the pit of the stomach, which is also known under the name of heartburn. While pyrosis is of frequent occurrence in hyperchlorhydria, it may also appear as a neurosis even if the gastric secretion is perfectly normal. It is generally believed that the sensation of heartburn can be produced solely by acid fluids, but the sensation can exist even without the presence of an acid. Thus I have at present under observation a patient with achylia gastrica. in whom the gastric contents are almost always of a neutral reaction and who nevertheless frequently complains of heartburn.