Some twenty years ago there lived in Berlin an old misanthrope named Wilhelm von Osten. He was a man with a small private income, a little eccentric in his ways and obsessed by one idea, the intelligence of animals. He began by undertaking the education of a horse that gave him no very definite results. But, in 1900, he became the owner of a Russian stallion who, under the name of Hans, to which was soon added the Homeric and well-earned prefix of Kluge, or Clever, was destined to upset all our notions of animal psychology and to raise questions that rank among the most unexpected and the most absorbing problems which man has yet encountered. Thanks to Von Osten, whose patience, contrary to what one might think, was in no wise angelic but resembled rather a frenzied obstinacy, the horse made rapid and extraordinary progress. This progress is very aptly described by Professor E. Clarapede, of the university of Geneva, who says, in his excellent monograph on the Elberfeld horses: "After making him familiar with various common ideas, such as right, left, top, bottom and so on, his master began to teach him arithmetic by the intuitive method. Hans was brought to a table on which were placed first one, then two, then several small skittles. Von Osten, kneeling beside Hans, uttered the corresponding numbers, at the same time making him strike as many blows with his hoof as there were skittles on the table. Before long, the skittles were replaced by figures written on a blackboard. The results were astonishing. The horse was capable not only of counting (that is to say, of striking as many blows as he was asked), but also of himself making real calculations, of solving little problems. . . . "But Hans could do more than mere sums: he knew how to read; he was a musician, distinguishing between harmonious and dissonant chords. He also had an extraordinary memory: he could tell the date of each day of the current week. In short, he got through all the tasks which an intelligent schoolboy of fourteen is able to perform." 2