The pack-mule should be active, short-coupled, short-legged, small-boned, square-built, with manifest powers of endurance, and should weigh from 800 to 1000 pounds. Army Regulations state that "mules purchased for the army by the Quartermaster's Department should conform to the following conditions: They should be strong, stout, compact, sound, and kind; free from defects in every particular; from four to nine years old; from 850 to 1200 pounds in weight; from 14 to 16 hands high, and suitable in all respects for the transportation service of the army. If for draught purposes, they are to be well broken to harness; if for pack purposes, they need not be broken, and the standard of height may be reduced to 13½ hands, if the animal be in other respects suitable. "Every animal will be branded with the letters U. S. on the left fore shoulder on the day he is received. A complete descriptive list will be made of each animal at the time of purchase, which will accompany him wherever he may be transferred." Under ordinary circumstances none but gentle, well-broken mules from four to eight years old should be purchased. New mules should be handled with the greatest patience, care, and kindness until they become thoroughly accustomed to the new service required of them. All violence must be avoided, for mules are naturally timid and easily startled, and for this reason men of good temper should be employed in breaking them; any rough treatment is sure to lead to delay in the training and may cause irretrievable harm. =Age.=--Ordinary limit 15 to 16 years; many live to 20, some to 30, years. From 8 to 12 he is in his prime. Age is told by teeth, as with horses. =Sex.=--Females are generally to be preferred to males for mountain-batteries, being, as a rule, more docile and better shaped. =Pace.=--A battery-mule can walk four miles an hour. The average transport-mule walks a little over three miles an hour. A mule's pace is slow down but quick up hill. Mules show fatigue in their gait by drooping the head; the neck becomes horizontal and the ears droop back; the ordinary carriage of the latter is erect and forward; when the mule begins to fan them, he is probably tired. =Condition.=--They should be kept in hard condition--not fat. =Watering.=--They will ordinarily refuse hard or bad water; and sometimes decline to drink merely from fancy, and will water from a bucket when not from the stream. By throwing a handful of grass into the bucket of water, they may generally be induced to drink. They may be watered on the march, even when hot, if kept in motion afterward. Where there are leeches in a stream, be careful not to water too close to the bank.