There was a serious aspect to the situation, however, that the military authorities could not overlook. Besides being a source of discomfort, the louse is the sole carrier of one of the most dread diseases that afflict mankind--typhus fever. In bygone times typhus was known variously as army fever, camp fever, or jail fever. It was particularly prevalent in this country at the time of the Revolution, and it existed to some extent here during the Civil War--an indication of what must have been the condition of individual American soldiers in those days. Typhus exists to-day practically as an endemic on the central plateau of Mexico, the range of the disease touching the border of the United States. The disease cannot invade this country, however, because of the lack of carriers. But if the A. E. F. had returned to the United States with its 2,000,000 men lice-infested, the demobilized soldiers might have distributed typhus carriers from one end of the country to the other and exposed the nation to a terrible menace. The sanitary regulations of the A. E. F. kept typhus away from the troops by controlling the lice. The Quartermaster Corps operated a number of mobile delousing plants just behind the front lines and in the billeting areas to the rear. It is interesting to note that these plants had to be camouflaged because the airmen of the enemy sometimes mistook them for batteries of artillery and directed gunfire upon them. As these plants increased in number and efficiency they reduced the lousiness of the combat troops to a scant 3 per cent. As long as our troops remained in France largely billeted on the French population, it was unlikely that the field sanitary measures could extinguish the louse altogether; but the command of the expedition determined that at the ports of embarkation the American doughboy should bid good-bye to _P. vestimenti_ forever. The importance of completely delousing the troops was emphasized in the same G. H. Q. memorandum that had set up the embarkation system.