The next best place for study purposes is a spacious, sanitary and well-stocked zoological park, wherein are assembled great collections of the most interesting land vertebrates that can be procured, from all over the earth. There the student can observe many new traits of wild animal character, as they are brought to the surface by captivity. There will some individuals reveal the worst traits of their species. Others will reveal marvels in mentality, and teach lessons such as no man can learn from them in the open. To study temperament, there is no place like a zoo. Even there, however, the wisest course,--as it seems to me,--is not to introduce too many appliances as aids to mental activity, but rather to see what the animal subject thinks and does _by its own initiative._ In the testing of memory and the perceptive faculties, training for performances is the best method to pursue. The reader has a right to know that the author of this volume has enjoyed unparalleled opportunities for the observation and study of highly intelligent wild animals, both in their wild haunts and in a great vivarium; and these combined opportunities have covered a long series of years. Before proceeding farther, it is desirable to define certain terms that frequently will be used in these pages. THE ANIMAL BRAIN is the generator of the mind, and the clearing- house of the senses. As a mechanism, the brain of man is the most perfect, and in the descent through the mammals, birds, reptiles, amphibians and fishes, the brain progressively is simplified in form and function. THOUGHT is the result of the various processes of the brain and nervous system, stimulated by the contributions of the senses. SANITY is the state of normal, orderly and balanced thought, as formulated by a healthy brain. INSANITY is a state of mental disease, resulting in disordered, unbalanced and chaotic thought, destitute of reason. REASON is the manifestation of correct observation and healthful thought which recognizes both cause and effect, and leads from premise to conclusion. INTELLIGENCE is created by the possession of knowledge either inherited or acquired. It may be either latent or active; and it is the forerunner of reason. INSTINCT is the knowledge or impulse which animals or men derive from their ancestors by inheritance, and which they obey, either consciously or subconsciously in working out their own preservation, increase and betterment. Instinct often functions as a sixth sense. EDUCATION is the acquirement of knowledge by precept or by observation; but animals as well as men may be self-taught, and become self-educated, by the diligent exercise of the observing and reasoning faculties. The adjustment of a wild animal mind to conditions unknown to its ancestors is through the process of self-education, and by logical reasoning from premise to conclusion. The wild animal must think, or die.