As soon as the brackets were made secure, Dohong turned his attention to the two large sleeping boxes which were built very solidly on the balcony of his cage. Both of those structures he tore completely to pieces,--always working with the utmost good nature and cheerfulness. Realizing that they could not exist in the cage with him, we gave him a permit to tear them out--and save the time of the carpenters. Dohong's use of his lever was seen by hundreds of visitors, and one frequent visitor to the Park, Mr. L. A. Camacho, an engineer, was so much impressed that he published in the _Scientific American_ an illustrated account of what he saw. For a long period, Dohong had been more or less annoyed by the fact that he could not get his head out between the front bars of his cage, and look around the partition into the home of his next- door neighbor. Very soon after he discovered the use of the lever, he swung his trapeze bar out to the upper corner of his cage, thrust the end of it out between the first bar and the steel column of the partition, and very deftly bent two of the iron bars outward far enough so that he could easily thrust his head outside and have his coveted look. One of our later and largest orangs made a specialty of twisting the straw of his bedding into a rope six or seven feet long, then throwing it over his trapeze bar and swinging by it, forward and back. Time and space will not permit the enumeration of the various things done by that ape of mechanical mind with his swinging rope and his trapeze, with ropes of straw _twisted by himself,_ with keys, locks, hammer, nails and boxes. Any man who can witness such manifestations as those described above, and deny the existence in the animal of an ability to reason from cause to effect, must be prepared to deny the evidence of his own senses. The individual variations between orangs, as also between chimpanzees, are great and striking. It may with truth be said that no two individuals of either species are really quite alike in physiognomy, temperament and mental capacity. As subjects for the experimental psychologist, it is difficult to see how any other could be found that would be even a good second in living interest to the great apes. The facts thus far recorded, so I believe, present only a suggestion of the rich results that await the patient scientific investigator. In the year 1915 Dr. Robert M. Yerkes, of Harvard University, conducted at Montecito, southern California, in a comfortable primate laboratory, six months of continuous and diligent experiments on the behavior of orang-utans and monkeys. His report, published under the title of "The Mental Life of Monkeys and Apes: A Study of Ideational Behavior," is a document of much interest and value. Dr. Yerkes' use of the orang-utan as a subject was a decided step forward in the study of "animal behavior" in America. IX THE MAN-LIKENESS OF THE CHIMPANZEE