II. On the contrary, we hold, with Goethe, that “matter cannot exist and be operative without spirit, nor spirit without matter.” We adhere firmly to the pure, unequivocal monism of Spinoza: Matter, or infinitely extended substance, and spirit (or energy), or sensitive and thinking substance, are the two fundamental attributes or principal properties of the all-embracing divine essence of the world, the universal substance. (Cf. [chap. xii].)
[CHAPTER II]
OUR BODILY FRAME
Fundamental Importance of Anatomy—Human Anatomy—Hippocrates, Aristotle, Galen, Vesalius—Comparative Anatomy—Georges Cuvier—Johannes Müller—Karl Gegenbaur—Histology—The Cellular Theory—Schleiden and Schwann—Kölliker—Virchow—Man a Vertebrate, a Tetrapod, a Mammal, a Placental, a Primate—Prosimiæ and Simiæ—The Catarrhinæ—Papiomorphic and Anthropomorphic Apes—Essential Likeness of Man and the Ape in Corporal Structure
All biological research, all investigation into the forms and vital activities of organisms, must first deal with the visible body, in which the morphological and physiological phenomena are observed. This fundamental rule holds good for man just as much as for all other living things. Moreover, the inquiry must not confine itself to mere observation of the outer form; it must penetrate to the interior, and study both the general plan and the minute details of the structure. The science which pursues this fundamental investigation in the broadest sense is anatomy.
The first stimulus to an inquiry into the human frame arose, naturally, in medicine. As it was usually practised by the priests in the older civilizations, we may assume that these highest representatives of the education of the time had already acquired a certain amount of anatomical knowledge two thousand years before Christ, or even earlier. We do not, however, find more exact observations, founded on the dissection of mammals, and applied, by analogy, to the human frame, until we come to the Greek scientists of the sixth and fifth centuries before Christ—Empedocles (of Agrigentum) and Democritus (of Abdera), and especially the most famous physician of classic antiquity, Hippocrates (of Cos). It was from these and other sources that the great Aristotle, the renowned “father of natural history,” equally comprehensive as investigator and philosopher, derived his first knowledge. After him only one anatomist of any consequence is found in antiquity, the Greek physician Claudius Galenus (of Pergamus), who developed a wealthy practice in Rome in the second century after Christ, under the Emperor Marcus Aurelius. All these ancient anatomists acquired their knowledge, as a rule, not by the dissection of the human body itself—which was then sternly forbidden—but by a study of the bodies of the animals which most closely resembled man, especially the apes; they were all, indeed, comparative anatomists.
The triumph of Christianity and its mystic theories meant retrogression to anatomy, as it did to all the other sciences. The popes were resolved above all things to detain humanity in ignorance; they rightly deemed a knowledge of the human organism to be a dangerous source of enlightenment as to our true nature. During the long period of thirteen centuries the writings of Galen were almost the only source of human anatomy, just as the works of Aristotle were for the whole of natural history. It was not until the sixteenth century, when the spiritual tyranny of the papacy was broken by the Reformation, and the geocentric theory, so intimately connected with papal doctrine, was destroyed by the new cosmic system of Copernicus, that the knowledge of the human frame entered upon a new period of progress. The great anatomists, Vesalius (of Brussels), and Eustachius and Fallopius (of Modena), advanced the knowledge of our bodily structure so much by their own thorough investigations that little remained for their numerous followers to do, with regard to the more obvious phenomena, except the substantiation of details. Andreas Vesalius, as courageous as he was talented and indefatigable, was the pioneer of the movement; he completed in his twenty-eighth year (1543) that great and systematic work De humani corporis fabrica; he gave to the whole of human anatomy a new and independent scope and a more solid foundation. On that account he was, at a later date, at Madrid—where he was physician to Charles V. and Philip II.—condemned to death by the Inquisition as a magician. He only escaped by undertaking a pilgrimage to Jerusalem; in returning he suffered shipwreck on the Isle of Zante, and died there in misery and destitution.
The great merit of the nineteenth century, as far as our knowledge of the human frame is concerned, lies in the founding of two new lines of research of immense importance—comparative anatomy and histology, or microscopic anatomy. The former was intimately associated with human anatomy from the very beginning; indeed, it had to supply the place of the latter so long because the dissection of human corpses was a crime visited with capital punishment—that was the case even in the fifteenth century! But the many anatomists of the next three centuries devoted themselves mainly to a more accurate study of the human organism. The elaborate science which we now call comparative anatomy was born in the year 1803, when the great French zoologist Georges Cuvier (a native of Mömpelgard, in Alsace) published his profound Leçons sur l’anatomie comparée, and endeavored to formulate, for the first time, definite laws as to the organism of man and the beasts. While his predecessors—among whom was Goethe in 1790—had mainly contented themselves with comparing the skeleton of man with those of other animals, Cuvier’s broader vision took in the whole of the animal organization. He distinguished therein four great and mutually independent types: Vertebrata, Articulata, Mollusca, and Radiata. This advance was of extreme consequence for our “question of all questions,” since it clearly brought out the fact that man belonged to the vertebral type, and differed fundamentally from all the other types. It is true that the keen-sighted Linné had already, in his Systema Natuae, made a great step in advance by assigning man a definite place in the class of mammals; he had even drawn up the three groups of half-apes, apes, and men (Lemur, simia, and homo) in the order of primates. But his keen, systematic mind was not furnished with that profound empirical foundation, supplied by comparative anatomy, which Cuvier was the first to attain. Further developments were added by the great comparative anatomists of our own century—Friedrich Meckel (Halle), Johannes Müller (Berlin), Richard Owen, T. Huxley, and Karl Gegenbaur (Jena, subsequently Heidelberg). The last-named, in applying the evolutionary theory, which Darwin had just established, to comparative anatomy, raised his science to the front rank of biological studies. The numerous comparative anatomical works of Gegenbaur are, like his well-known Manual of Human Anatomy, equally distinguished by a thorough empirical acquaintance with their immense multitudes of facts, and by a comprehensive control of his material, and its philosophic appreciation in the evolutionary sense. His recent Comparative Anatomy of the Vertebrata establishes the solid foundation on which our conviction of the vertebral character of man in every aspect is chiefly based.
Microscopic anatomy has been developed, in the course of the present century, in a very different fashion from comparative anatomy. At the beginning of the century (1802) a French physician, Bichat, made an attempt to dissect the organs of the human body into their finer constituents by the aid of the microscope, and to show the connection of these various tissues (hista, or tela). This first attempt led to little result, because the scientist was ignorant of the one common element of all the different tissues. This was first discovered (1838) in the shape of the cell, in the plant world, by Matthias Schleiden, and immediately afterwards proved to be the same in the animal world by Theodor Schwann, the pupil and assistant of Johannes Müller at Berlin. Two other distinguished pupils of this great master, who are still living, Albert Kölliker and Rudolph Virchow, took up the cellular theory, and the theory of tissues which is founded on it, in the sixties, and applied them to the human organism in all its details, both in health and disease; they proved that, in man and all other animals, every tissue is made up of the same microscopic particles, the cells, and these “elementary organisms” are the real, self-active citizens which, in combinations of millions, constitute the “cellular state,” our body. All these cells spring from one simple cell, the cytula, or impregnated ovum, by continuous subdivision. The general structure and combination of the tissues are the same in man as in the other vertebrates. Among these the mammals, the youngest and most highly developed class take precedence, in virtue of certain special features which were acquired late. Such are, for instance, the microscopic texture of the hair, of the glands of the skin, and of the breasts, and the corpuscles of the blood, which are quite peculiar to mammals, and different from those of the other vertebrates; man, even in these finest histological relations, is a true mammal.