the most violent opposition in an isolated department of neurophysiology, namely, that of psychology. The wonderful "soul of man" was thought to be a peculiar "being," and it today seems to many impossible that it should have been historically developed from the "soul of the ape." But in the first place the wonderful discoveries of comparative anatomy during the last ten years inform us for the first time that the minute as well as the gross structure of the brain of man is the same as that of the anthropoid apes, the unimportant difference in shape and size of single parts that exists between the two being less than the corresponding difference between the anthropoid and the lowest apes of the Old World, especially such as the baboons. Secondly, comparative ontogeny teaches us that the very highly complex brain of man has developed out of the same rudimentary form as that of all other vertebrate animals—out of five cerebral vesicles of the embryo that lie one behind the other. The special way and method by which the peculiar form of the primate brain is developed out of this extremely simple rudiment is found to be exactly the same in man as in the anthropoid apes. Thirdly, comparative physiology shows us by observation and experiment that the total functions of the brain, even consciousness and the so-called higher mental faculties, together with reflex acts, are in man preceded by the same physical and chemical phenomena as in all other mammals. Fourthly and lastly, we learn through comparative pathology that all so-called "mental diseases" in man are determined by material changes in the material of the brain, just as they are in the nearest related mammals.
An unprejudiced critical comparison confirms here also Huxley's law: the psychological differences between man and the anthropoid apes are less than the corresponding differences between the anthropoid and the lowest apes. And this physiological fact corresponds exactly with the results of an anatomical examination of the differences found in the structure of the cortex of the brain, the most important "organ of the soul." The deep significance of this information will be clearer to us when we consider the extraordinary differences in mental capacity that exist within the human species itself. There we see, high above, a Goethe and a Shakespeare, a Darwin and a Lamarck, a Spinoza and an Aristotle, and then, far below, a Veddah and an Akkah, a Bushman and a Patagonian. The enormous difference in mental capacity between these highest and lowest representatives of the human race is much greater than between the latter and the anthropoid apes.
Since, in spite of this, we find that the soul of man is to-day regarded in the widest circles as an especial, "being" and as the most important witness against the decried doctrine of the descent of man from apes, we explain it on the one hand by the wretched condition of the so-called "psychology," on the other by the widespread superstition concerning the immortality of the soul. The science which to-day in most text-
