Pharmacological action of Senecio riddellii.

The administration of the crude alkaloid of Senecio riddellii in mice produced acute intoxication followed by remission, recurrence of symptoms, and death. The toxic dose was determined by intraperitoneal and oral administration of the alkaloid. The feeding of plant produced typical symptoms of chronic poisoning similar to that observed in cattle. The alkaloid‐free resinous residue produced vascular damage in the intestinal tract with subsequent development of gangrene. The injection of the crude alkaloid of Senecio riddellii reduced the vitamin A content of the liver.