This subject is important for three reasons: Carbon monoxid is liberated by bursting shells and therefore is one of the gases responsible for mortality in the present war. Deaths, accidental and suicidal, from inhalation of illuminating gas are increasingly frequent in civil life.1Henderson2states that carbon monoxid causes more deaths than all other gases combined. There is a reason to believe that a higher carbon monoxid content in illuminating gas is in part responsible for this. Statistics of certain cities of Great Britain3indicate that the higher percentage of such deaths parallels the greater proportion of water gas used in the manufacture of a cheaper product. Carbon monoxid poisoning is of medicolegal significance. A history is not always available, and the characteristic cherry-red color of the blood and chemi-cal proof of carbon monoxid are aids to diagnosis only in the first few days after poisoning. Kolisko4in