This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
When taken into the stomach, as it usually is, in aqueous solution, carbonic acid is refreshing and thirst-quenching. It somewhat increases the gastrointestinal secretions, and excites their peristaltic action, but diminishes the sensibility of the mucous membrane. A moderate quantity improves appetite, but an over-dose lessens it. No such serious symptoms follow, however, as after inhalation of the gas by the lungs.