In respect to the merely alkaline properties, there is a close correspondence between potassium and sodium, but as regards other properties there is a wide divergence. The salts of soda are alkaline, and hence neutralize the acid of the gastric juice. They are readily diffusible. Like the potash salts, they increase the alkalinity of the blood, and under suitable conditions determine a change in the urine from acid to alkaline. The same results follow the administration during or between the intervals of digestion, as in the case of the potash salts. The alkalinity of the urine induced by soda salts ceases on the day following their administration, and the acidity is then increased. Soda has but little toxic action besides the local caustic effects. Caustic soda, like caustic potash, dissolves albumen, forms soaps with fats, and destroys the tissues widely and deeply. It is, however, less active than caustic potash. The composition of the blood does not appear to be altered by the salts of soda in any reasonable quantity. Laborde, in some comparative experiments between chlorate of potassa and chlorate of soda, finds that the latter, in treble the quantity of the former, has but a transient effect, depressing the temperature half a degree, and causing a slight salivation, but producing none of the paralytic symptoms which follow the administration of the potash salts. Guttmann had previously demonstrated the same facts, and Schonlein, in some studies with the carbonate, finds that even in large doses in frogs it rarely arrests the heart's movements, only slowing and lengthening the contractions. Chloride of sodium has, unquestionably, an important office in the economy. It forms the principal part of the soluble constituents of the ash of all animal substances. Albumen owes its solubility in part to the chloride of sodium; it dissolves pure casein, and impedes the coagulation of the fibrin of the blood. In one thousand parts of blood there are about four parts of this salt. It is very abundant in various normal secretions and pathological products. The gastric juice is very rich in chloride of sodium, and it probably is the source of the hydrochloric acid of the stomach (Lehmann). In the course of an inflammation, notably of pneumonia, the chloride of sodium of the system accumulates in the inflamed area, and disappears from the urine. Its return to the urine is in the nature of a critical phenomenon, and marks the subsidence of the inflammation. The importance of this salt in the animal economy is doubtless the cause of the universal taste; all in excess of the needs of the body is excreted, chiefly by the kidneys, and with such facility that no accumulation takes place. While a necessary amount is of high importance and excess is readily disposed of, it is probable that long and habitual indulgence in a considerable excess increases waste and lowers the vital forces.