When Rosas, that man of "blood and iron," was Dictator of the Argentine country--a position which he held for a quarter of a century--desertors from the army were inexorably shot when caught, as they generally were. But where my boyhood was spent there was a deserter, a man named Santa Anna, who for seven years, without ever leaving the neighbourhood of his home, succeeded in eluding his pursuers by means of the marvellous sagacity and watchful care exercised by his horse. When taking his rest on the plain--for he seldom slept under a roof--his faithful horse kept guard. At the first sight of mounted men on the horizon he would fly to his master, and, seizing his cloak between his teeth, rouse him with a vigorous shake. The hunted man would start up, and in a moment man and horse would vanish into one of the dense reed-beds abounding in the place, and where no man could follow. I have not space to tell more about this horse; but at last, in the fulness of time, when the figs were ripe--literally as well as figuratively, for it happened in the autumn of the year--the long tyrannous rule ended, and Santa Anna came out of the reed-beds, where he had lived his wild-animal life, to mix with his fellows. I knew him some years later. He was a rather heavy-looking man, with little to say, and his reputation for honesty was not good in the place; but I dare say there was something good in him. Students of nature are familiar with the modifying effects of new conditions on man and brute. Take, for example, the gaucho: he must every day traverse vast distances, see quickly, judge rapidly, be ready at all times to encounter hunger and fatigue, violent changes of temperature, great and sudden perils. These conditions have made him differ widely from the peasant of the Peninsula; he has the endurance and keen sight of a wolf, is fertile in expedients, quick in action, values human life not at all, and is in pain or defeat a Stoic. Unquestionably the horse he rides has also suffered a great change. He differs as much from the English hunter, for instance, as one animal can well differ from another of the same species. He never pounds the earth and wastes his energies in vain parade. He has not the dauntless courage that performs such brilliant feats in the field, and that often as not attempts the impossible. In the chase he husbands all his strength, carrying his head low, and almost grazing the ground with his hoofs, so that he is not a showy animal. Constant use, or the slow cumulative process of natural selection, has served to develop a keenness of sense almost preternatural. The vulture's eye, with all the advantage derived from the vulture's vast elevation above the scene surveyed, is not so far-reaching as the sense of smell in the pampa horse. A common phenomenon on the pampas is a sudden migration of the horses of a district to some distant place. This occurs in seasons of drought, when grass or water fails.