However, within a comparatively short time after American troops got into the front line it was realized that a second mask, inferior in protection to the first, was highly undesirable. During a gas attack men seemed to acquire an uncontrollable desire to shift from one mask to the other. This shifting in nearly every case resulted in a casualty. We then came rapidly to the conclusion that one mask only should be furnished, and that one the best that could be made, and then to impress upon the soldier the fact that his life depended upon the care he took of his mask. This proved to be an entirely sound conclusion, as the number of men gassed through injuries to the mask was comparatively small. An interesting proof of the value the soldier placed upon his mask was shown by the articles of equipment thrown away by 10,000 British stragglers in the great German offensive of March, 1918. Of the articles thus thrown away the gas mask came at the foot of the list, with only 800 missing. The steel helmet is said to have come next with about 4,000 missing. SIZES OF FACES FOR MASKS When adopting the British respirator in August, 1917, it was decided that the American face as well as the American stature was probably larger than the English. Accordingly inquiry was made in regard to the sizes of masks issued to the Canadians as it was thought probable they required a greater proportion of the larger size masks than did the English. When prescribing the relative quantities of each size of mask to be furnished Americans, the Canadian requirements were taken as a base but with the larger sizes increased slightly over the Canadian requirements. As a matter of fact even these increases proved considerably too small, so that the numbers in the two sizes above normal had to be finally more than doubled. OBJECTIONS TO GERMAN TYPE MASK The American Gas Service felt from the beginning that a design which attached the box of chemicals to the facepiece was unsound in principle (this design was used in the German mask and in the French A. R. S. masks), since it did not allow proper flexibility for increasing the size of the box to care for new gases. Furthermore, the weight of the box during movement caused the facepiece to swing slightly from side to side. This interfered with vision and tended to lift the facepiece away from the face and allow gas to enter. That the objections of the American Gas Service to this type were correct was proved by the difficulty encountered toward the end of the war by both the French and the Germans in trying to provide a suitable filter for protection against particulate clouds and the smokes, such as stannic chloride and diphenylchloroarsine. STRUGGLE BETWEEN MASK AND GAS