Plate IX from "An Atlas of Gas Poisoning" by the American Red Cross and Medical Research Committee (American Red Cross, 1918). Plate title: "Ulceration of trachea by mustard gas." Text begins: "The characteristic feature is the sloughing of the tracheal mucous membrane. The reddening of the base of the tongue and of the pharynx with a sharp delimitation where the oesophagus has refused ingress to the toxic vapour, is also seen with chlorine and other irritant gases. ... " The American Red Cross published this guide for the American Expeditionary Force in World War I, sometimes called the "chemists’ war." The chromolithograph plates of characteristic injuries were intended to help inexperienced officers identify the type of gas used in attacks.