Phosphoric acid occurs both in the organized and inorganized kingdoms. It is obtained by distilling together phosphorus and nitric acid in distilled water. The United States Pharmacopoeia gives the exact proportions and describes the mode of operating. We have some excellent provings of this agent furnished by Hahnemann. Krumsieg experimented with it in heroic doses. He took forty grains of dilute phosphoric acid at one dose, gradually in- creasing to two drachms, after which he was attacked with a painful -cough and had to discontinue his provings. The stool became more 116 ACIDUM PHOSPHORICUM. fluid and scanty ; from the nose issued a peculiar odor like that of phosphoric acid. CEREBRO-SPINAL GEOUP. This acid has caused a dull headache, with buzzing in the head ; crampy pains in both parietal bones as if the sides of the head were pressed together ; tearing, drawing and stitching pains in the head or in one side of the head ; painful shocks in the head. These pains are of the nature of nervous headache or hemicrania, where, how- ever, we have very little clinical experience to show with this acid.