Late studies upon the growth of the embryo of anthropoid apes have shown that they were at certain periods almost indistinguishable from human embryos. Another proof, quite striking and interesting, is in the similarity of the parasites and dis-eases of men and apes. Scientists have, within the past few years, made a series of comparative investigations upon the blood and serum of men and apes, which have resulted in most remarkable discoveries. There are certain accurate tests known to the physiological chemist by which human blood may be distinguished from the blood of all other animals, but the blood of these man-like apes is an exception to this, and cannot be distinguished from human blood. [Sidenote: Difference in the development of man and apes] From these facts it is clear that the earlier types of men were creatures whose physical development and whose habits were not very different from those of apes. The development that has taken place since that time is truly very wonderful and has resulted in a widening gap between man and apes that today seems very great. The truth remains, however, that this gap is not so much one of anatomy and physiology as it is one of mentality and of external habits and material aids to living that have resulted from man's greatly developed mental faculties. [Sidenote: Power of speech a factor in man's evolution] Thus, when the mind of man reached the stage of development in which the use of articulate speech became possible, the evolution of intelligence proceeded at a very much more rapid pace than had been possible before. He could communicate his ideas to his fellow-creatures; concerted action became possible, and the faculty of reason, or the ability to think was multiplied by the number of beings who could communicate with each other. The power of reason and the ability to communicate ideas resulted in the formation of those habits which distinguish man from other animals. When one primitive man learned the use of a club as a weapon, found how to use sharp-edged stones as cutting tools, or discovered the wonders and power of fire, he communicated his new-found knowledge to the other members of his tribe, with the result that new ideas became common property. [Sidenote: Man's bad habits have kept pace with his progress] This spreading of habits or customs took place very rapidly among men and was the source of the various changes which distinguished civilized life from savage life. But we must here point out that not only good habits were so spread, but bad ones as well. The origin and the use of opium and of alcohol, the injuries of fashionable dress and the economic wrongs of tyrannical government originated along with the birth of language, art, science, and all that uplifts and benefits mankind.