This is an abstract of lectures delivered at the Chemical Warfare School and the Army Medical School. The author's conclusions as to the effects and humaneness of gas warfare are quite generally known. The astounding fact is presented that 65,038,810 men were mobilized by the countries participating in the World War, and of these 8,543,515 were killed in battle or died from wounds or disease contracted in the war. The number of gas casualties was 1,009,038, 78,390 being killed or dying from the effects of gas. Of the 2,039,329 men in the American army who arrived in France, 110 out of every 1,000 were admitted to hospital as the result of battle injuries and 6¾ died as the result of these injuries. The heaviest loss was suffered by the infantry; the signal corps was second. The American troops did not suffer from many cloud attacks, but the British suffered a