It must be confessed that this mystery, springing from a point where we least expected to come upon the unknown, bears enough within itself to scatter all our convictions. Remember that, since man appeared upon this earth, he has lived among creatures which, from immemorial experience, he thought that he knew as perfectly as he knows an object fashioned by his hands. Out of these creatures he chose the most docile and, as he called them, the most intelligent, attaching in this case to the word intelligence a sense so narrow as to be almost ridiculous. He observed them, scrutinized them, tried them, analyzed them and dissected them in every imaginable way; and whole lives were devoted to nothing but the study of their habits, their faculties, their nervous system, their pathology, their psychology, their instincts. All this led to certainties which, among those supported by our unexplained little existence on an inexplicable planet, would seem to be the least doubtful, the least subject to revision. There is no disputing, for instance, that the horse is gifted with an extraordinary memory, that he possesses the sense of direction, that he understands a few signs and even a few words and that he obeys them. It is equally undeniable that the anthropoid apes are capable of imitating a great number of our actions and of our attitudes: but it is also manifest that their bewildered and feverish imagination perceives neither their object nor their scope. As for the dog, the one of all these privileged animals who lives closest to us, who for thousands and thousands of years has eaten at our table and worked with us and been our friend, it is manifest that, now and then, we catch a rather uncanny gleam in his deep, watchful eyes. It is certain that he sometimes wanders in a curious fashion along the mysterious border that separates our own intelligence from that which we grant to the other creatures inhabiting this earth with us. But it is no less certain that he has never definitely passed it. We know exactly how far he can go; and we have invariably found that our efforts, our patience, our encouragement, our passionate appeals, have hitherto failed to draw him out of the somewhat narrow, darkly enchanted circle wherein nature seems to have imprisoned him once and for all. 20