A first or second lieutenant of the Chemical Warfare Service poses in his M1917 tunic with the CWS insignia on the collar. The peaked cap is the M1905 model with a bronze eagle on the front. Formerly the U.S. Army Gas Service, the Chemical Warfare Service contained the Pyrotechnic Section, which experimented with Livens projectors and flamethrowers. Note the long, unkempt fingernails on this young officer's left hand.