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.
Moderate doses tend to improve the tone and functional power of the stomach, and, as already remarked, this acid irritates much less, even after continued use, than the other inorganic acids; large or concentrated doses, however, taken by the mouth, may cause gastroenteritis, and after death, redness, erosion, and ecchymoses have been found in the stomach and duodenum (Monk and Leyden). When Pavy injected 1 to 2 oz. into the stomach of dogs it was quickly rejected, but on passing it into the duodenum, a saccharine condition of the urine and the blood was produced, just as after intravenous injections. After toxic doses, fatty degeneration has been found in the liver, kidneys, and muscular tissue.
The same as for other mineral acids (v. p. 196).