The thesis presents a systematic chemical investigation of the active principles of the ava root (Piper methysticum), beginning with historical uses and continuing through detailed laboratory methods for extraction and resin separation. It identifies distinct resin fractions and characterizes their metallic salts, oxidation products, and associated acidic components, and isolates neutral crystalline methysticin and related methysticinic acid. Analytical sections examine alcohol radicals and oxidative transformations, and a physiological chapter summarizes observed pharmacological effects. The conclusion synthesizes chemical findings and their relation to the root's narcotic and toxic properties.