Although it is likely that many efforts have been made to domesticate the other larger felines, no distinct success has attended these experiments. A large Asiatic cat known as the chetah is somewhat used in hunting for sport, but the species has never been adopted in any definite way. In fact, with all the larger cats, including the lion, which is structurally a little apart from the other members of the group, the size and furious nature of the animal have made it impossible to begin the process of selection which has been the means whereby the wilderness motive has been replaced by that of the household in the case of all other domesticated beasts. THE HORSE Value of the Strength of the Horse to Man.--Origin of the Horse.--Peculiar Advantage of the Solid Hoof.--Domestication of the Horse.--How begun.--Use as a Pack Animal.--For War.--Peculiar Advantages of the Animal for Use of Men.--Mental Peculiarities.--Variability of Body.--Spontaneous Variations due to Climate.--Variations of Breeds.--Effect of the Invention of Horseshoes.--Donkeys and Mules compared with Horse.--Especial Value of these Animals.--Diminishing Value of Horses in Modern Civilization.--Continued Need of their Service in War. The largest economic problem which primitive people on their way upward towards civilization had unconsciously to face was that of obtaining some kind of strength which could be added to the power of their own weak limbs. For all his eminent capacities of body, man is not a strong animal, nor is he so built that he can apply the measure of strength that is in him to good advantage. There are scores if not hundreds of species with which he came in contact in his effort to dominate nature that are stronger, swifter, and better provided with natural weapons. With the first step upward, as in almost all the succeeding steps, the advance depended on securing more energy than that with which our kind was directly endowed. It is hardly too much to say that the progress of mankind beyond the savage state would probably never have been effected but for the bodily help which has been rendered by a few domesticated animals.