The mules sent to the Mexican possessions from our western states, Missouri, Tennessee, and Kentucky, are considered of much more value than such as are bred from the native (usually wild) mares. The difference probably arises, in part, from the Mexicans using jacks so inferior to most of the stock animals used by the citizens of those states. Mare mules are estimated in those regions at one-third more than horse mules. The reason assigned for this is, that after a day's journey of excessive fatigue, there is a larger quantity of blood secreted in the bladder, which the female, owing to her larger passage, voids at once, and without much apparent suffering, while the male does not get rid of it, frequently, till after an hour of considerable pain. The effect of this difference is seen in the loss of flesh and strength in the male to an extent far beyond that of the female. _The method of reducing refractory mules_ in the northern Mexican possessions, is for the person to grasp them firmly by the ears, while another whips them severely on the fore-legs and belly. _Estimated annual saving to the United States from the employment of mules in the place of horses._--To sum up the advantages of working mules over horses, we shall have as advantages: 1. They are more easily, surely, and cheaply raised. 2. They are maintained, after commencing work, for much less than the cost of keeping horses. 3. They are not subject to many of the diseases of the horse, and to others only in a mitigated degree, and even these are easily cured in the mule. 4. They attain a greater age, and their average working years are probably twice that of the horse. In 1840, there were reported to be 4,335,669 horses and mules in the Union, no discrimination having been made between them. Suppose the total number at the present time is 4,650,000, and that of these 650,000 are mules. If we deduct one-fourth, supposed to be required for the purposes of breed, fancy-horses, &c., we shall have 3,000,000 horses, whose places may be equally well supplied by the same number of mules. We have seen that Mr. Hood, of Maryland, estimates the expense of a working horse at $44 per annum, (not an over estimate for the Atlantic states,) while that of the mule is $22. The difference is $22, which it is proper to reduce to meet the much lower rate of keeping at the West. If we put the difference at $10, we shall find the saving in the keep, shoeing, farriery, &c., by substituting mules for the 3,000,000 horses that can be dispensed with, will be $30,000,000 per annum. But this is not all.