release time:2023-12-07 07:21:21 source:complement each other author:{typename type="name"/}
STRABO THE GEOGRAPHER The earliest of these workers in point of time is Strabo. This most famous of ancient geographers was born in Amasia, Pontus, about 63 B.C., and lived to the year 24 A.D., living, therefore, in the age of Caesar and Augustus, during which the final transformation in the political position of the kingdom of Egypt was effected. The name of Strabo in a modified form has become popularized through a curious circumstance. The geographer, it appears, was afflicted with a peculiar squint of the eyes, hence the name strabismus, which the modern oculist applies to that particular infirmity. Fortunately, the great geographer has not been forced to depend upon hearsay evidence for recognition. His comprehensive work on geography has been preserved in its entirety, being one of the few expansive classical writings of which this is true. The other writings of Strabo, however, including certain histories of which reports have come down to us, are entirely lost. The geography is in many ways a remarkable book. It is not, however, a work in which any important new principles are involved. Rather is it typical of its age in that it is an elaborate compilation and a critical review of the labors of Strabo's predecessors. Doubtless it contains a vast deal of new information as to the details of geography--precise areas and distance, questions of geographical locations as to latitude and zones, and the like. But however important these details may have been from a contemporary stand-point, they, of course, can have nothing more than historical interest to posterity. The value of the work from our present stand-point is chiefly due to the criticisms which Strabo passes upon his forerunners, and to the incidental historical and scientific references with which his work abounds. Being written in this closing period of ancient progress, and summarizing, as it does, in full detail the geographical knowledge of the time, it serves as an important guide-mark for the student of the progress of scientific thought. We cannot do better than briefly to follow Strabo in his estimates and criticisms of the work of his predecessors, taking note thus of the point of view from which he himself looked out upon the world. We shall thus gain a clear idea as to the state of scientific geography towards the close of the classical epoch. "If the scientific investigation of any subject be the proper avocation of the philosopher," says Strabo, "geography, the science of which we propose to treat, is certainly entitled to a high place; and this is evident from many considerations. They who first undertook to handle the matter were distinguished men. Homer, Anaximander the Milesian, and Hecaeus (his fellow-citizen according to Eratosthenes), Democritus, Eudoxus, Dicaearchus, and Ephorus, with many others, and after these, Eratosthenes, Polybius, and Posidonius, all of them philosophers. Nor is the great learning through which alone this subject can be approached possessed by any but a person acquainted with both human and divine things, and these attainments constitute what is called philosophy. In addition to its vast importance in regard to social life and the art of government, geography unfolds to us a celestial phenomena, acquaints us with the occupants of the land and ocean, and the vegetation, fruits, and peculiarities of the various quarters of the earth, a knowledge of which marks him who cultivates it as a man earnest in the great problem of life and happiness." Strabo goes on to say that in common with other critics, including Hipparchus, he regards Homer as the first great geographer. He has much to say on the geographical knowledge of the bard, but this need not detain us. We are chiefly concerned with his comment upon his more recent predecessors, beginning with Eratosthenes. The constant reference to this worker shows the important position which he held. Strabo appears neither as detractor nor as partisan, but as one who earnestly desires the truth. Sometimes he seems captious in his criticisms regarding some detail, nor is he always correct in his emendations of the labors of others; but, on the whole, his work is marked by an evident attempt at fairness. In reading his book, however, one is forced to the conclusion that Strabo is an investigator of details, not an original thinker. He seems more concerned with precise measurements than with questionings as to the open problems of his science. Whatever he accepts, then, may be taken as virtually the stock doctrine of the period. "As the size of the earth," he says, "has been demonstrated by other writers, we shall here take for granted and receive as accurate what they have advanced. We shall also assume that the earth is spheroidal, that its surface is likewise spheroidal and, above all, that bodies have a tendency towards its centre, which latter point is clear to the perception of the most average understanding. However, we may show summarily that the earth is spheroidal, from the consideration that all things, however distant, tend to its centre, and that every body is attracted towards its centre by gravity. This is more distinctly proved from observations of the sea and sky, for here the evidence of the senses and common observation is alone requisite. The convexity of the sea is a further proof of this to those who have sailed, for they cannot perceive lights at a distance when placed at the same level as their eyes, and if raised on high they at once become perceptible to vision though at the same time farther removed. So when the eye is raised it sees what before was utterly imperceptible. Homer speaks of this when he says:
" 'Lifted up on the vast wave he quickly beheld afar.' Sailors as they approach their destination behold the shore continually raising itself to their view, and objects which had at first seemed low begin to lift themselves. Our gnomons, also, are, among other things, evidence of the revolution of the heavenly bodies, and common-sense at once shows us that if the depth of the earth were infinite such a revolution could not take place."[1] Elsewhere Strabo criticises Eratosthenes for having entered into a long discussion as to the form of the earth. This matter, Strabo thinks, "should have been disposed of in the compass of a few words." Obviously this doctrine of the globe's sphericity had, in the course of 600 years, become so firmly established among the Greek thinkers as to seem almost axiomatic. We shall see later on how the Western world made a curious recession from this seemingly secure position under stimulus of an Oriental misconception. As to the size of the globe, Strabo is disposed to accept without particular comment the measurements of Eratosthenes. He speaks, however, of "more recent measurements," referring in particular to that adopted by Posidonius, according to which the circumference is only about one hundred and eighty thousand stadia. Posidonius, we may note in passing, was a contemporary and friend of Cicero, and hence lived shortly before the time of Strabo. His measurement of the earth was based on observations of a star which barely rose above the southern horizon at Rhodes as compared with the height of the same star when observed at Alexandria. This measurement of Posidonius, together with the even more famous measurement of Eratosthenes, appears to have been practically the sole guide as to the size of the earth throughout the later periods of antiquity, and, indeed, until the later Middle Ages. As becomes a writer who is primarily geographer and historian rather than astronomer, Strabo shows a much keener interest in the habitable portions of the globe than in the globe as a whole. He assures us that this habitable portion of the earth is a great island, "since wherever men have approached the termination of the land, the sea, which we designate ocean, has been met with, and reason assures us of the similarity of this place which our senses have not been tempted to survey." He points out that whereas sailors have not circumnavigated the globe, that they had not been prevented from doing so by any continent, and it seems to him altogether unlikely that the Atlantic Ocean is divided into two seas by narrow isthmuses so placed as to prevent circumnavigation. "How much more probable that it is confluent and uninterrupted. This theory," he adds, "goes better with the ebb and flow of the ocean. Moreover (and here his reasoning becomes more fanciful), the greater the amount of moisture surrounding the earth, the easier would the heavenly bodies be supplied with vapor from thence." Yet he is disposed to believe, following Plato, that the tradition "concerning the island of Atlantos might be received as something more than idle fiction, it having been related by Solon, on the authority of the Egyptian priests, that this island, almost as large as a continent, was formerly in existence although now it had disappeared."[2] In a word, then, Strabo entertains no doubt whatever that it would be possible to sail around the globe from Spain to India. Indeed, so matter-of-fact an inference was this that the feat of Columbus would have seemed less surprising in the first century of our era than it did when actually performed in the fifteenth century. The terrors of the great ocean held the mariner back, rather than any doubt as to where he would arrive at the end of the voyage. Coupled with the idea that the habitable portion of the earth is an island, there was linked a tolerably definite notion as to the shape of this island. This shape Strabo likens to a military cloak. The comparison does not seem peculiarly apt when we are told presently that the length of the habitable earth is more than twice its breadth. This idea, Strabo assures us, accords with the most accurate observations "both ancient and modern." These observations seemed to show that it is not possible to live in the region close to the equator, and that, on the other hand, the cold temperature sharply limits the habitability of the globe towards the north. All the civilization of antiquity clustered about the Mediterranean, or extended off towards the east at about the same latitude. Hence geographers came to think of the habitable globe as having the somewhat lenticular shape which a crude map of these regions suggests. We have already had occasion to see that at an earlier day Anaxagoras was perhaps influenced in his conception of the shape of the earth by this idea, and the constant references of Strabo impress upon us the thought that this long, relatively narrow area of the earth's surface is the only one which can be conceived of as habitable. Strabo had much to tell us concerning zones, which, following Posidonius, he believes to have been first described by Parmenides. We may note, however, that other traditions assert that both Thales and Pythagoras had divided the earth into zones. The number of zones accepted by Strabo is five, and he criticises Polybius for making the number six. The five zones accepted by Strabo are as follows: the uninhabitable torrid zone lying in the region of the equator; a zone on either side of this extending to the tropic; and then the temperate zones extending in either direction from the tropic to the arctic regions. There seems to have been a good deal of dispute among the scholars of the time as to the exact arrangement of these zones, but the general idea that the north-temperate zone is the part of the earth with which the geographer deals seemed clearly established. That the south-temperate zone would also present a habitable area is an idea that is sometimes suggested, though seldom or never distinctly expressed. It is probable that different opinions were held as to this, and no direct evidence being available, a cautiously scientific geographer like Strabo would naturally avoid the expression of an opinion regarding it. Indeed, his own words leave us somewhat in doubt as to the precise character of his notion regarding the zones. Perhaps we shall do best to quote them: "Let the earth be supposed to consist of five zones. (1) The equatorial circle described around it. (2) Another parallel to this, and defining the frigid zone of the northern hemisphere. (3) A circle passing through the poles and cutting the two preceding circles at right- angles. The northern hemisphere contains two quarters of the earth, which are bounded by the equator and circle passing through the poles. Each of these quarters should be supposed to contain a four-sided district, its northern side being of one-half of the parallel next the pole, its southern by the half of the equator, and its remaining sides by two segments of the circle drawn through the poles, opposite to each other, and equal in length. In one of these (which of them is of no consequence) the earth which we inhabit is situated, surrounded by a sea and similar to an island. This, as we said before, is evident both to our senses and to our reason. But let any one doubt this, it makes no difference so far as geography is concerned whether you believe the portion of the earth which we inhabit to be an island or only admit what we know from experience --namely, that whether you start from the east or the west you may sail all around it. Certain intermediate spaces may have been left (unexplored), but these are as likely to be occupied by sea as uninhabited land. The object of the geographer is to describe known countries. Those which are unknown he passes over equally with those beyond the limits of the inhabited earth. It will, therefore, be sufficient for describing the contour of the island we have been speaking of, if we join by a right line the outmost points which, up to this time, have been explored by voyagers along the coast on either side."[3] We may pass over the specific criticisms of Strabo upon various explorations that seem to have been of great interest to his contemporaries, including an alleged trip of one Eudoxus out into the Atlantic, and the journeyings of Pytheas in the far north. It is Pytheas, we may add, who was cited by Hipparchus as having made the mistaken observation that the length of the shadow of the gnomon is the same at Marseilles and Byzantium, hence that these two places are on the same parallel. Modern commentators have defended Pytheas as regards this observation, claiming that it was Hipparchus and not Pytheas who made the second observation from which the faulty induction was drawn. The point is of no great significance, however, except as showing that a correct method of determining the problems of latitude had thus early been suggested. That faulty observations and faulty application of the correct principle should have been made is not surprising. Neither need we concern ourselves with the details as to the geographical distances, which Strabo found so worthy of criticism and controversy. But in leaving the great geographer we may emphasize his point of view and that of his contemporaries by quoting three fundamental principles which he reiterates as being among the "facts established by natural philosophers." He tells us that "(1) The earth and heavens are spheroidal. (2) The tendency of all bodies having weight is towards a centre. (3) Further, the earth being spheroidal and having the same centre as the heavens, is motionless, as well as the axis that passes through both it and the heavens. The heavens turn round both the earth and its axis, from east to west. The fixed stars turn round with it at the same rate as the whole. These fixed stars follow in their course parallel circles, the principal of which are the equator, two tropics, and the arctic circles; while the planets, the sun, and the moon describe certain circles comprehended within the zodiac."[4] Here, then, is a curious mingling of truth and error. The Pythagorean doctrine that the earth is round had become a commonplace, but it would appear that the theory of Aristarchus, according to which the earth is in motion, has been almost absolutely forgotten. Strabo does not so much as refer to it; neither, as we shall see, is it treated with greater respect by the other writers of the period.
TWO FAMOUS EXPOSITORS--PLINY AND PTOLEMY While Strabo was pursuing his geographical studies at Alexandria, a young man came to Rome who was destined to make his name more widely known in scientific annals than that of any other Latin writer of antiquity. This man was Plinius Secundus, who, to distinguish him from his nephew, a famous writer in another field, is usually spoken of as Pliny the Elder. There is a famous story to the effect that the great Roman historian Livy on one occasion addressed a casual associate in the amphitheatre at Rome, and on learning that the stranger hailed from the outlying Spanish province of the empire, remarked to him, "Yet you have doubtless heard of my writings even there." "Then," replied the stranger, "you must be either Livy or Pliny." The anecdote illustrates the wide fame which the Roman naturalist achieved in his own day. And the records of the Middle Ages show that this popularity did not abate in succeeding times. Indeed, the Natural History of Pliny is one of the comparatively few bulky writings of antiquity that the efforts of copyists have preserved to us almost entire. It is, indeed, a remarkable work and eminently typical of its time; but its author was an industrious compiler, not a creative genius. As a monument of industry it has seldom been equalled, and in this regard it seems the more remarkable inasmuch as Pliny was a practical man of affairs who occupied most of his life as a soldier fighting the battles of the empire. He compiled his book in the leisure hours stolen from sleep, often writing by the light of the camp-fire. Yet he cites or quotes from about four thousand works, most of which are known to us only by his references. Doubtless Pliny added much through his own observations. We know how keen was his desire to investigate, since he lost his life through attempting to approach the crater of Vesuvius on the occasion of that memorable eruption which buried the cities of Herculaneum and Pompeii. Doubtless the wandering life of the soldier had given Pliny abundant opportunity for personal observation in his favorite fields of botany and zoology. But the records of his own observations are so intermingled with knowledge drawn from books that it is difficult to distinguish the one from the other. Nor does this greatly matter, for whether as closet-student or field-naturalist, Pliny's trait of mind is essentially that of the compiler. He was no philosophical thinker, no generalizer, no path-maker in science. He lived at the close of a great progressive epoch of thought; in one of those static periods when numberless observers piled up an immense mass of details which might advantageously be sorted into a kind of encyclopaedia. Such an encyclopaedia is the so-called Natural History of Pliny. It is a vast jumble of more or less uncritical statements regarding almost every field of contemporary knowledge. The descriptions of animals and plants predominate, but the work as a whole would have been immensely improved had the compiler shown a more critical spirit. As it is, he seems rather disposed to quote any interesting citation that he comes across in his omnivorous readings, shielding himself behind an equivocal "it is said," or "so and so alleges." A single illustration will suffice to show what manner of thing is thought worthy of repetition. "It is asserted," he says, "that if the fish called a sea-star is smeared with the fox's blood and then nailed to the upper lintel of the door, or to the door itself, with a copper nail, no noxious spell will be able to obtain admittance, or, at all events, be productive of any ill effects." It is easily comprehensible that a work fortified with such practical details as this should have gained wide popularity. Doubtless the natural histories of our own day would find readier sale were they to pander to various superstitions not altogether different from that here suggested. The man, for example, who believes that to have a black cat cross his path is a lucky omen would naturally find himself attracted by a book which took account of this and similar important details of natural history. Perhaps, therefore, it was its inclusion of absurdities, quite as much as its legitimate value, that gave vogue to the celebrated work of Pliny. But be that as it may, the most famous scientist of Rome must be remembered as a popular writer rather than as an experimental worker. In the history of the promulgation of scientific knowledge his work is important; in the history of scientific principles it may virtually be disregarded.
PTOLEMY, THE LAST GREAT ASTRONOMER OF ANTIQUITY Almost the same thing may be said of Ptolemy, an even more celebrated writer, who was born not very long after the death of Pliny. The exact dates of Ptolemy's life are not known, but his recorded observations extend to the year 151 A.D. He was a working astronomer, and he made at least one original discovery of some significance--namely, the observation of a hitherto unrecorded irregularity of the moon's motion, which came to be spoken of as the moon's evection. This consists of periodical aberrations from the moon's regular motion in its orbit, which, as we now know, are due to the gravitation pull of the sun, but which remained unexplained until the time of Newton. Ptolemy also made original observations as to the motions of the planets. He is, therefore, entitled to a respectable place as an observing astronomer; but his chief fame rests on his writings. His great works have to do with geography and astronomy. In the former field he makes an advance upon Strabo, citing the latitude of no fewer than five thousand places. In the field of astronomy, his great service was to have made known to the world the labors of Hipparchus. Ptolemy has been accused of taking the star-chart of his great predecessor without due credit, and indeed it seems difficult to clear him of this charge. Yet it is at least open to doubt whether be intended any impropriety, inasmuch as be all along is sedulous in his references to his predecessor. Indeed, his work might almost be called an exposition of the astronomical doctrines of Hipparchus. No one pretends that Ptolemy is to be compared with the Rhodesian observer as an original investigator, but as a popular expounder his superiority is evidenced in the fact that the writings of Ptolemy became practically the sole astronomical text-book of the Middle Ages both in the East and in the West, while the writings of Hipparchus were allowed to perish. The most noted of all the writings of Ptolemy is the work which became famous under the Arabic name of Almagest. This word is curiously derived from the Greek title
GALEN--THE LAST GREAT ALEXANDRIAN There is one other field of scientific investigation to which we must give brief attention before leaving the antique world. This is the field of physiology and medicine. In considering it we shall have to do with the very last great scientist of the Alexandrian school. This was Claudius Galenus, commonly known as Galen, a man whose fame was destined to eclipse that of all other physicians of antiquity except Hippocrates, and whose doctrines were to have the same force in their field throughout the Middle Ages that the doctrines of Aristotle had for physical science. But before we take up Galen's specific labors, it will be well to inquire briefly as to the state of medical art and science in the Roman world at the time when the last great physician of antiquity came upon the scene. The Romans, it would appear, had done little in the way of scientific discoveries in the field of medicine, but, nevertheless, with their practicality of mind, they had turned to better account many more of the scientific discoveries of the Greeks than did the discoverers themselves. The practising physicians in early Rome were mostly men of Greek origin, who came to the capital after the overthrow of the Greeks by the Romans. Many of them were slaves, as earning money by either bodily or mental labor was considered beneath the dignity of a Roman citizen. The wealthy Romans, who owned large estates and numerous slaves, were in the habit of purchasing some of these slave doctors, and thus saving medical fees by having them attend to the health of their families. By the beginning of the Christian era medicine as a profession had sadly degenerated, and in place of a class of physicians who practised medicine along rational or legitimate lines, in the footsteps of the great Hippocrates, there appeared great numbers of "specialists," most of them charlatans, who pretended to possess supernatural insight in the methods of treating certain forms of disease. These physicians rightly earned the contempt of the better class of Romans, and were made the object of many attacks by the satirists of the time. Such specialists travelled about from place to place in much the same manner as the itinerant "Indian doctors" and "lightning tooth-extractors" do to-day. Eye-doctors seem to have been particularly numerous, and these were divided into two classes, eye-surgeons and eye-doctors proper. The eye-surgeon performed such operations as cauterizing for ingrowing eyelashes and operating upon growths about the eyes; while the eye-doctors depended entirely upon salves and lotions. These eye-salves were frequently stamped with the seal of the physician who compounded them, something like two hundred of these seals being still in existence. There were besides these quacks, however, reputable eye-doctors who must have possessed considerable skill in the treatment of certain ophthalmias. Among some Roman surgical instruments discovered at Rheims were found also some drugs employed by ophthalmic surgeons, and an analysis of these show that they contained, among other ingredients, some that are still employed in the treatment of certain affections of the eye. One of the first steps taken in recognition of the services of physicians was by Julius Caesar, who granted citizenship to all physicians practising in Rome. This was about fifty years before the Christian era, and from that time on there was a gradual improvement in the attitude of the Romans towards the members of the medical profession. As the Romans degenerated from a race of sturdy warriors and became more and more depraved physically, the necessity for physicians made itself more evident. Court physicians, and physicians-in-ordinary, were created by the emperors, as were also city and district physicians. In the year 133 A.D. Hadrian granted immunity from taxes and military service to physicians in recognition of their public services. The city and district physicians, known as the archiatri populaires, treated and cared for the poor without remuneration, having a position and salary fixed by law and paid them semi-annually. These were honorable positions, and the archiatri were obliged to give instruction in medicine, without pay, to the poor students. They were allowed to receive fees and donations from their patients, but not, however, until the danger from the malady was past. Special laws were enacted to protect them, and any person subjecting them to an insult was liable to a fine "not exceeding one thousand pounds." An example of Roman practicality is shown in the method of treating hemorrhage, as described by Aulus Cornelius Celsus (53 B.C. to 7 A.D.). Hippocrates and Hippocratic writers treated hemorrhage by application of cold, pressure, styptics, and sometimes by actual cauterizing; but they knew nothing of the simple method of stopping a hemorrhage by a ligature tied around the bleeding vessel. Celsus not only recommended tying the end of the injured vessel, but describes the method of applying two ligatures before the artery is divided by the surgeon--a common practice among surgeons at the present time. The cut is made between these two, and thus hemorrhage is avoided from either end of the divided vessel. Another Roman surgeon, Heliodorus, not only describes the use of the ligature in stopping hemorrhage, but also the practice of torsion--twisting smaller vessels, which causes their lining membrane to contract in a manner that produces coagulation and stops hemorrhage. It is remarkable that so simple and practical a method as the use of the ligature in stopping hemorrhage could have gone out of use, once it had been discovered; but during the Middle Ages it was almost entirely lost sight of, and was not reintroduced until the time of Ambroise Pare, in the sixteenth century. Even at a very early period the Romans recognized the advantage of surgical methods on the field of battle. Each soldier was supplied with bandages, and was probably instructed in applying them, something in the same manner as is done now in all modern armies. The Romans also made use of military hospitals and had established a rude but very practical field-ambulance service. "In every troop or bandon of two or four hundred men, eight or ten stout fellows were deputed to ride immediately behind the fighting-line to pick up and rescue the wounded, for which purpose their saddles had two stirrups on the left side, while they themselves were provided with water-flasks, and perhaps applied temporary bandages. They were encouraged by a reward of a piece of gold for each man they rescued. 'Noscomi' were male nurses attached to the military hospitals, but not inscribed 'on strength' of the legions, and were probably for the most part of the servile class."[6] From the time of the early Alexandrians, Herophilus and Erasistratus, whose work we have already examined, there had been various anatomists of some importance in the Alexandrian school, though none quite equal to these earlier workers. The best-known names are those of Celsus (of whom we have already spoken), who continued the work of anatomical investigation, and Marinus, who lived during the reign of Nero, and Rufus of Ephesus. Probably all of these would have been better remembered by succeeding generations had their efforts not been eclipsed by those of Galen. This greatest of ancient anatomists was born at Pergamus of Greek parents. His father, Nicon, was an architect and a man of considerable ability. Until his fifteenth year the youthful Galen was instructed at home, chiefly by his father; but after that time he was placed under suitable teachers for instruction in the philosophical systems in vogue at that period. Shortly after this, however, the superstitious Nicon, following the interpretations of a dream, decided that his son should take up the study of medicine, and placed him under the instruction of several learned physicians. Galen was a tireless worker, making long tours into Asia Minor and Palestine to improve himself in pharmacology, and studying anatomy for some time at Alexandria. He appears to have been full of the superstitions of the age, however, and early in his career made an extended tour into western Asia in search of the chimerical "jet-stone"--a stone possessing the peculiar qualities of "burning with a bituminous odor and supposed to possess great potency in curing such diseases as epilepsy, hysteria, and gout." By the time he had reached his twenty-eighth year he had perfected his education in medicine and returned to his home in Pergamus. Even at that time he had acquired considerable fame as a surgeon, and his fellow-citizens showed their confidence in his ability by choosing him as surgeon to the wounded gladiators shortly after his return to his native city. In these duties his knowledge of anatomy aided him greatly, and he is said to have healed certain kinds of wounds that had previously baffled the surgeons. In the time of Galen dissections of the human body were forbidden by law, and he was obliged to confine himself to dissections of the lower animals. He had the advantage, however, of the anatomical works of Herophilus and Erasistratus, and he must have depended upon them in perfecting his comparison between the anatomy of men and the lower animals. It is possible that he did make human dissections surreptitiously, but of this we have no proof. He was familiar with the complicated structure of the bones of the cranium. He described the vertebrae clearly, divided them into groups, and named them after the manner of anatomists of to-day. He was less accurate in his description of the muscles, although a large number of these were described by him. Like all anatomists before the time of Harvey, he had a very erroneous conception of the circulation, although he understood that the heart was an organ for the propulsion of blood, and he showed that the arteries of the living animals did not contain air alone, as was taught by many anatomists. He knew, also, that the heart was made up of layers of fibres that ran in certain fixed directions--that is, longitudinal, transverse, and oblique; but he did not recognize the heart as a muscular organ. In proof of this he pointed out that all muscles require rest, and as the heart did not rest it could not be composed of muscular tissue. Many of his physiological experiments were conducted upon scientific principles. Thus he proved that certain muscles were under the control of definite sets of nerves by cutting these nerves in living animals, and observing that the muscles supplied by them were rendered useless. He pointed out also that nerves have no power in themselves, but merely conduct impulses to and from the brain and spinal-cord. He turned this peculiar knowledge to account in the case of a celebrated sophist, Pausanias, who had been under the treatment of various physicians for a numbness in the fourth and fifth fingers of his left hand. These physicians had been treating this condition by applications of poultices to the hand itself. Galen, being called in consultation, pointed out that the injury was probably not in the hand itself, but in the ulner nerve, which controls sensation in the fourth and fifth fingers. Surmising that the nerve must have been injured in some way, he made careful inquiries of the patient, who recalled that he had been thrown from his chariot some time before, striking and injuring his back. Acting upon this information, Galen applied stimulating remedies to the source of the nerve itself--that is, to the bundle of nerve-trunks known as the brachial plexus, in the shoulder. To the surprise and confusion of his fellow-physicians, this method of treatment proved effective and the patient recovered completely in a short time. Although the functions of the organs in the chest were not well understood by Galen, he was well acquainted with their anatomy. He knew that the lungs were covered by thin membrane, and that the heart was surrounded by a sac of very similar tissue. He made constant comparisons also between these organs in different animals, as his dissections were performed upon beasts ranging in size from a mouse to an elephant. The minuteness of his observations is shown by the fact that he had noted and described the ring of bone found in the hearts of certain animals, such as the horse, although not found in the human heart or in most animals. His description of the abdominal organs was in general accurate. He had noted that the abdominal cavity was lined with a peculiar saclike membrane, the peritoneum, which also surrounded most of the organs contained in the cavity, and he made special note that this membrane also enveloped the liver in a peculiar manner. The exactness of the last observation seems the more wonderful when we reflect that even to-day the medical, student finds a correct understanding of the position of the folds of the peritoneum one of the most difficult subjects in anatomy. As a practical physician he was held in the highest esteem by the Romans. The Emperor Marcus Aurelius called him to Rome and appointed him physician-inordinary to his son Commodus, and on special occasions Marcus Aurelius himself called in Galen as his medical adviser. On one occasion, the three army surgeons in attendance upon the emperor declared that he was about to be attacked by a fever. Galen relates how "on special command I felt his pulse, and finding it quite normal, considering his age and the time of day, I declared it was no fever but a digestive disorder, due to the food he had eaten, which must be converted into phlegm before being excreted. Then the emperor repeated three times, 'That's the very thing,' and asked what was to be done. I answered that I usually gave a glass of wine with pepper sprinkled on it, but for you kings we only use the safest remedies, and it will suffice to apply wool soaked in hot nard ointment locally. The emperor ordered the wool, wine, etc., to be brought, and I left the room. His feet were warmed by rubbing with hot hands, and after drinking the peppered wine, he said to Pitholaus (his son's tutor), 'We have only one doctor, and that an honest one,' and went on to describe me as the first of physicians and the only philosopher, for he had tried many before who were not only lovers of money, but also contentious, ambitious, envious, and malignant."[7] It will be seen from this that Galen had a full appreciation of his own abilities as a physician, but inasmuch as succeeding generations for a thousand years concurred in the alleged statement made by Marcus Aurelius as to his ability, he is perhaps excusable for his open avowal of his belief in his powers. His faith in his accuracy in diagnosis and prognosis was shown when a colleague once said to him, "I have used the prognostics of Hippocrates as well as you. Why can I not prognosticate as well as you?" To this Galen replied, "By God's help I have never been deceived in my prognosis."[8] It is probable that this statement was made in the heat of argument, and it is hardly to be supposed that he meant it literally. His systems of treatment were far in advance of his theories regarding the functions of organs, causes of disease, etc., and some of them are still first principles with physicians. Like Hippocrates, he laid great stress on correct diet, exercise, and reliance upon nature. "Nature is the overseer by whom health is supplied to the sick," he says. "Nature lends her aid on all sides, she decides and cures diseases. No one can be saved unless nature conquers the disease, and no one dies unless nature succumbs." From the picture thus drawn of Galen as an anatomist and physician, one might infer that he should rank very high as a scientific exponent of medicine, even in comparison with modern physicians. There is, however, another side to the picture. His knowledge of anatomy was certainly very considerable, but many of his deductions and theories as to the functions of organs, the cause of diseases, and his methods of treating them, would be recognized as absurd by a modern school-boy of average intelligence. His greatness must be judged in comparison with ancient, not with modern, scientists. He maintained, for example, that respiration and the pulse-beat were for one and the same purpose--that of the reception of air into the arteries of the body. To him the act of breathing was for the purpose of admitting air into the lungs, whence it found its way into the heart, and from there was distributed throughout the body by means of the arteries. The skin also played an important part in supplying the body with air, the pores absorbing the air and distributing it through the arteries. But, as we know that he was aware of the fact that the arteries also contained blood, he must have believed that these vessels contained a mixture of the two. Modern anatomists know that the heart is divided into two approximately equal parts by an impermeable septum of tough fibres. Yet, Galen, who dissected the hearts of a vast number of the lower animals according to his own account, maintained that this septum was permeable, and that the air, entering one side of the heart from the lungs, passed through it into the opposite side and was then transferred to the arteries. He was equally at fault, although perhaps more excusably so, in his explanation of the action of the nerves. He had rightly pointed out that nerves were merely connections between the brain and spinal-cord and distant muscles and organs, and had recognized that there were two kinds of nerves, but his explanation of the action of these nerves was that "nervous spirits" were carried to the cavities of the brain by blood-vessels, and from there transmitted through the body along the nerve-trunks. In the human skull, overlying the nasal cavity, there are two thin plates of bone perforated with numerous small apertures. These apertures allow the passage of numerous nerve-filaments which extend from a group of cells in the brain to the delicate membranes in the nasal cavity. These perforations in the bone, therefore, are simply to allow the passage of the nerves. But Galen gave a very different explanation. He believed that impure "animal spirits" were carried to the cavities of the brain by the arteries in the neck and from there were sifted out through these perforated bones, and so expelled from the body. He had observed that the skin played an important part in cooling the body, but he seems to have believed that the heart was equally active in overheating it. The skin, therefore, absorbed air for the purpose of "cooling the heart," and this cooling process was aided by the brain, whose secretions aided also in the cooling process. The heart itself was the seat of courage; the brain the seat of the rational soul; and the liver the seat of love. The greatness of Galen's teachings lay in his knowledge of anatomy of the organs; his weakness was in his interpretations of their functions. Unfortunately, succeeding generations of physicians for something like a thousand years rejected the former but clung to the latter, so that the advances he had made were completely overshadowed by the mistakes of his teachings.
XI. A RETROSPECTIVE GLANCE AT CLASSICAL SCIENCE It is a favorite tenet of the modern historian that history is a continuous stream. The contention has fullest warrant. Sharp lines of demarcation are an evidence of man's analytical propensity rather than the work of nature. Nevertheless it would be absurd to deny that the stream of history presents an ever-varying current. There are times when it seems to rush rapidly on; times when it spreads out into a broad--seemingly static--current; times when its catastrophic changes remind us of nothing but a gigantic cataract. Rapids and whirlpools, broad estuaries and tumultuous cataracts are indeed part of the same stream, but they are parts that vary one from another in their salient features in such a way as to force the mind to classify them as things apart and give them individual names. So it is with the stream of history; however strongly we insist on its continuity we are none the less forced to recognize its periodicity. It may not be desirable to fix on specific dates as turning-points to the extent that our predecessors were wont to do. We may not, for example, be disposed to admit that the Roman Empire came to any such cataclysmic finish as the year 476 A.D., when cited in connection with the overthrow of the last Roman Empire of the West, might seem to indicate. But, on the other hand, no student of the period can fail to realize that a great change came over the aspect of the historical stream towards the close of the Roman epoch. The span from Thales to Galen has compassed about eight hundred years--let us say thirty generations. Throughout this period there is scarcely a generation that has not produced great scientific thinkers--men who have put their mark upon the progress of civilization; but we shall see, as we look forward for a corresponding period, that the ensuing thirty generations produced scarcely a single scientific thinker of the first rank. Eight hundred years of intellectual activity --thirty generations of greatness; then eight hundred years of stasis--thirty generations of mediocrity; such seems to be the record as viewed in perspective. Doubtless it seemed far different to the contemporary observer; it is only in reasonable perspective that any scene can be viewed fairly. But for us, looking back without prejudice across the stage of years, it seems indisputable that a great epoch came to a close at about the time when the barbarian nations of Europe began to sweep down into Greece and Italy. We are forced to feel that we have reached the limits of progress of what historians are pleased to call the ancient world. For about eight hundred years Greek thought has been dominant, but in the ensuing period it is to play a quite subordinate part, except in so far as it influences the thought of an alien race. As we leave this classical epoch, then, we may well recapitulate in brief its triumphs. A few words will suffice to summarize a story the details of which have made up our recent chapters. In the field of cosmology, Greek genius has demonstrated that the earth is spheroidal, that the moon is earthlike in structure and much smaller than our globe, and that the sun is vastly larger and many times more distant than the moon. The actual size of the earth and the angle of its axis with the ecliptic have been measured with approximate accuracy. It has been shown that the sun and moon present inequalities of motion which may be theoretically explained by supposing that the earth is not situated precisely at the centre of their orbits. A system of eccentrics and epicycles has been elaborated which serves to explain the apparent motions of the heavenly bodies in a manner that may be called scientific even though it is based, as we now know, upon a false hypothesis. The true hypothesis, which places the sun at the centre of the planetary system and postulates the orbital and axial motions of our earth in explanation of the motions of the heavenly bodies, has been put forward and ardently championed, but, unfortunately, is not accepted by the dominant thinkers at the close of our epoch. In this regard, therefore, a vast revolutionary work remains for the thinkers of a later period. Moreover, such observations as the precession of the equinoxes and the moon's evection are as yet unexplained, and measurements of the earth's size, and of the sun's size and distance, are so crude and imperfect as to be in one case only an approximation, and in the other an absurdly inadequate suggestion. But with all these defects, the total achievement of the Greek astronomers is stupendous. To have clearly grasped the idea that the earth is round is in itself an achievement that marks off the classical from the Oriental period as by a great gulf. In the physical sciences we have seen at least the beginnings of great things. Dynamics and hydrostatics may now, for the first time, claim a place among the sciences. Geometry has been perfected and trigonometry has made a sure beginning. The conception that there are four elementary substances, earth, water, air, and fire, may not appear a secure foundation for chemistry, yet it marks at least an attempt in the right direction. Similarly, the conception that all matter is made up of indivisible particles and that these have adjusted themselves and are perhaps held in place by a whirling motion, while it is scarcely more than a scientific dream, is, after all, a dream of marvellous insight. In the field of biological science progress has not been so marked, yet the elaborate garnering of facts regarding anatomy, physiology, and the zoological sciences is at least a valuable preparation for the generalizations of a later time. If with a map before us we glance at the portion of the globe which was known to the workers of the period now in question, bearing in mind at the same time what we have learned as to the seat of labors of the various great scientific thinkers from Thales to Galen, we cannot fail to be struck with a rather startling fact, intimations of which have been given from time to time--the fact, namely, that most of the great Greek thinkers did not live in Greece itself. As our eye falls upon Asia Minor and its outlying islands, we reflect that here were born such men as Thales, Anaximander, Anaximenes, Heraclitus, Pythagoras, Anaxagoras, Socrates, Aristarchus, Hipparchus, Eudoxus, Philolaus, and Galen. From the northern shores of the aegean came Lucippus, Democritus, and Aristotle. Italy, off to the west, is the home of Pythagoras and Xenophanes in their later years, and of Parmenides and Empedocles, Zeno, and Archimedes. Northern Africa can claim, by birth or by adoption, such names as Euclid, Apollonius of Perga, Herophilus, Erasistratus, Aristippus, Eratosthenes, Ctesibius, Hero, Strabo, and Ptolemy. This is but running over the list of great men whose discoveries have claimed our attention. Were we to extend the list to include a host of workers of the second rank, we should but emphasize the same fact. All along we are speaking of Greeks, or, as they call themselves, Hellenes, and we mean by these words the people whose home was a small jagged peninsula jutting into the Mediterranean at the southeastern extremity of Europe. We think of this peninsula as the home of Greek culture, yet of all the great thinkers we have just named, not one was born on this peninsula, and perhaps not one in five ever set foot upon it. In point of fact, one Greek thinker of the very first rank, and one only, was born in Greece proper; that one, however, was Plato, perhaps the greatest of them all. With this one brilliant exception (and even he was born of parents who came from the provinces), all the great thinkers of Greece had their origin at the circumference rather than the centre of the empire. And if we reflect that this circumference of the Greek world was in the nature of the case the widely circling region in which the Greek came in contact with other nations, we shall see at once that there could be no more striking illustration in all history than that furnished us here of the value of racial mingling as a stimulus to intellectual progress. But there is one other feature of the matter that must not be overlooked. Racial mingling gives vitality, but to produce the best effect the mingling must be that of races all of which are at a relatively high plane of civilization. In Asia Minor the Greek mingled with the Semite, who had the heritage of centuries of culture; and in Italy with the Umbrians, Oscans, and Etruscans, who, little as we know of their antecedents, have left us monuments to testify to their high development. The chief reason why the racial mingling of a later day did not avail at once to give new life to Roman thought was that the races which swept down from the north were barbarians. It was no more possible that they should spring to the heights of classical culture than it would, for example, be possible in two or three generations to produce a racer from a stock of draught horses. Evolution does not proceed by such vaults as this would imply. Celt, Goth, Hun, and Slav must undergo progressive development for many generations before the population of northern Europe can catch step with the classical Greek and prepare to march forward. That, perhaps, is one reason why we come to a period of stasis or retrogression when the time of classical activity is over. But, at best, it is only one reason of several. The influence of the barbarian nations will claim further attention as we proceed. But now, for the moment, we must turn our eyes in the other direction and give attention to certain phases of Greek and of Oriental thought which were destined to play a most important part in the development of the Western mind--a more important part, indeed, in the early mediaeval period than that played by those important inductions of science which have chiefly claimed our attention in recent chapters. The subject in question is the old familiar one of false inductions or pseudoscience. In dealing with the early development of thought and with Oriental science, we had occasion to emphasize the fact that such false inductions led everywhere to the prevalence of superstition. In dealing with Greek science, we have largely ignored this subject, confining attention chiefly to the progressive phases of thought; but it must not be inferred from this that Greek science, with all its secure inductions, was entirely free from superstition. On the contrary, the most casual acquaintance with Greek literature would suffice to show the incorrectness of such a supposition. True, the great thinkers of Greece were probably freer from this thraldom. of false inductions than any of their predecessors. Even at a very early day such men as Xenophanes, Empedocles, Anaxagoras, and Plato attained to a singularly rationalistic conception of the universe. We saw that "the father of medicine," Hippocrates, banished demonology and conceived disease as due to natural causes. At a slightly later day the sophists challenged all knowledge, and Pyrrhonism became a synonym for scepticism in recognition of the leadership of a master doubter. The entire school of Alexandrians must have been relatively free from superstition, else they could not have reasoned with such effective logicality from their observations of nature. It is almost inconceivable that men like Euclid and Archimedes, and Aristarchus and Eratosthenes, and Hipparchus and Hero, could have been the victims of such illusions regarding occult forces of nature as were constantly postulated by Oriental science. Herophilus and Erasistratus and Galen would hardly have pursued their anatomical studies with equanimity had they believed that ghostly apparitions watched over living and dead alike, and exercised at will a malign influence. Doubtless the Egyptian of the period considered the work, of the Ptolemaic anatomists an unspeakable profanation, and, indeed, it was nothing less than revolutionary--so revolutionary that it could not be sustained in subsequent generations. We have seen that the great Galen, at Rome, five centuries after the time of Herophilus, was prohibited from dissecting the human subject. The fact speaks volumes for the attitude of the Roman mind towards science. Vast audiences made up of every stratum of society thronged the amphitheatre, and watched exultingly while man slew his fellow-man in single or in multiple combat. Shouts of frenzied joy burst from a hundred thousand throats when the death-stroke was given to a new victim. The bodies of the slain, by scores, even by hundreds, were dragged ruthlessly from the arena and hurled into a ditch as contemptuously as if pity were yet unborn and human life the merest bauble. Yet the same eyes that witnessed these scenes with ecstatic approval would have been averted in pious horror had an anatomist dared to approach one of the mutilated bodies with the scalpel of science. It was sport to see the blade of the gladiator enter the quivering, living flesh of his fellow-gladiator; it was joy to see the warm blood spurt forth from the writhing victim while he still lived; but it were sacrilegious to approach that body with the knife of the anatomist, once it had ceased to pulsate with life. Life itself was held utterly in contempt, but about the realm of death hovered the threatening ghosts of superstition. And such, be it understood, was the attitude of the Roman populace in the early and the most brilliant epoch of the empire, before the Western world came under the influence of that Oriental philosophy which was presently to encompass it. In this regard the Alexandrian world was, as just intimated, far more advanced than the Roman, yet even there we must suppose that the leaders of thought were widely at variance with the popular conceptions. A few illustrations, drawn from Greek literature at various ages, will suggest the popular attitude. In the first instance, consider the poems of Homer and of Hesiod. For these writers, and doubtless for the vast majority of their readers, not merely of their own but of many subsequent generations, the world is peopled with a multitude of invisible apparitions, which, under title of gods, are held to dominate the affairs of man. It is sometimes difficult to discriminate as to where the Greek imagination drew the line between fact and allegory; nor need we attempt to analyse the early poetic narratives to this end. It will better serve our present purpose to cite three or four instances which illustrate the tangibility of beliefs based upon pseudo-scientific inductions. Let us cite, for example, the account which Herodotus gives us of the actions of the Greeks at Plataea, when their army confronted the remnant of the army of Xerxes, in the year 479 B.C. Here we see each side hesitating to attack the other, merely because the oracle had declared that whichever side struck the first blow would lose the conflict. Even after the Persian soldiers, who seemingly were a jot less superstitious or a shade more impatient than their opponents, had begun the attack, we are told that the Greeks dared not respond at first, though they were falling before the javelins of the enemy, because, forsooth, the entrails of a fowl did not present an auspicious appearance. And these were Greeks of the same generation with Empedocles and Anaxagoras and aeschylus; of the same epoch with Pericles and Sophocles and Euripides and Phidias. Such was the scientific status of the average mind--nay, of the best minds--with here and there a rare exception, in the golden age of Grecian culture. Were we to follow down the pages of Greek history, we should but repeat the same story over and over. We should, for example, see Alexander the Great balked at the banks of the Hyphasis, and forced to turn back because of inauspicious auguries based as before upon the dissection of a fowl. Alexander himself, to be sure, would have scorned the augury; had he been the prey of such petty superstitions he would never have conquered Asia. We know how he compelled the oracle at Delphi to yield to his wishes; how he cut the Gordian knot; how he made his dominating personality felt at the temple of Ammon in Egypt. We know, in a word, that he yielded to superstitions only in so far as they served his purpose. Left to his own devices, he would not have consulted an oracle at the banks of the Hyphasis; or, consulting, would have forced from the oracle a favorable answer. But his subordinates were mutinous and he had no choice. Suffice it for our present purpose that the oracle was consulted, and that its answer turned the conqueror back. One or two instances from Roman history may complete the picture. Passing over all those mythical narratives which virtually constitute the early history of Rome, as preserved to us by such historians as Livy and Dionysius, we find so logical an historian as Tacitus recording a miraculous achievement of Vespasian without adverse comment. "During the months when Vespasian was waiting at Alexandria for the periodical season of the summer winds, and a safe navigation, many miracles occurred by which the favor of Heaven and a sort of bias in the powers above towards Vespasian were manifested." Tacitus then describes in detail the cure of various maladies by the emperor, and relates that the emperor on visiting a temple was met there, in the spirit, by a prominent Egyptian who was proved to be at the same time some eighty miles distant from Alexandria. It must be admitted that Tacitus, in relating that Vespasian caused the blind to see and the lame to walk, qualifies his narrative by asserting that "persons who are present attest the truth of the transaction when there is nothing to be gained by falsehood." Nor must we overlook the fact that a similar belief in the power of royalty has persisted almost to our own day. But no such savor of scepticism attaches to a narrative which Dion Cassius gives us of an incident in the life of Marcus Aurelius--an incident that has become famous as the episode of The Thundering Legion. Xiphilinus has preserved the account of Dion, adding certain picturesque interpretations of his own. The original narrative, as cited, asserts that during one of the northern campaigns of Marcus Aurelius, the emperor and his army were surrounded by the hostile Quadi, who had every advantage of position and who presently ceased hostilities in the hope that heat and thirst would deliver their adversaries into their hands without the trouble of further fighting. "Now," says Dion, "while the Romans, unable either to combat or to retreat, and reduced to the last extremity by wounds, fatigue, heat, and thirst, were standing helplessly at their posts, clouds suddenly gathered in great number and rain descended in floods--certainly not without divine intervention, since the Egyptian Maege Arnulphis, who was with Marcus Antoninus, is said to have invoked several genii by the aerial mercury by enchantment, and thus through them had brought down rain." Here, it will be observed, a supernatural explanation is given of a natural phenomenon. But the narrator does not stop with this. If we are to accept the account of Xiphilinus, Dion brings forward some striking proofs of divine interference. Xiphilinus gives these proofs in the following remarkable paragraph: "Dion adds that when the rain began to fall every soldier lifted his head towards heaven to receive the water in his mouth; but afterwards others hold out their shields or their helmets to catch the water for themselves and for their horses. Being set upon by the barbarians . . . while occupied in drinking, they would have been seriously incommoded had not heavy hail and numerous thunderbolts thrown consternation into the ranks of the enemy. Fire and water were seen to mingle as they left the heavens. The fire, however, did not reach the Romans, but if it did by chance touch one of them it was immediately extinguished, while at the same time the rain, instead of comforting the barbarians, seemed merely to excite like oil the fire with which they were being consumed. Some barbarians inflicted wounds upon themselves as though their blood had power to extinguish flames, while many rushed over to the side of the Romans, hoping that there water might save them." We cannot better complete these illustrations of pagan credulity than by adding the comment of Xiphilinus himself. That writer was a Christian, living some generations later than Dion. He never thought of questioning the facts, but he felt that Dion's interpretation of these facts must not go unchallenged. As he interprets the matter, it was no pagan magician that wrought the miracle. He even inclines to the belief that Dion himself was aware that Christian interference, and not that of an Egyptian, saved the day. "Dion knew," he declares, "that there existed a legion called The Thundering Legion, which name was given it for no other reason than for what came to pass in this war," and that this legion was composed of soldiers from Militene who were all professed Christians. "During the battle," continues Xiphilinus, "the chief of the Pretonians , had set at Marcus Antoninus, who was in great perplexity at the turn events were taking, representing to him that there was nothing the people called Christians could not obtain by their prayers, and that among his forces was a troop composed wholly of followers of that religion. Rejoiced at this news, Marcus Antoninus demanded of these soldiers that they should pray to their god, who granted their petition on the instant, sent lightning among the enemy and consoled the Romans with rain. Struck by this wonderful success, the emperor honored the Christians in an edict and named their legion The Thundering. It is even asserted that a letter existed by Marcus Antoninus on this subject. The pagans well knew that the company was called The Thunderers, having attested the fact themselves, but they revealed nothing of the occasion on which the leader received the name."[1] Peculiar interest attaches to this narrative as illustrating both credulousness as to matters of fact and pseudo-scientific explanation of alleged facts. The modern interpreter may suppose that a violent thunderstorm came up during the course of a battle between the Romans and the so-called barbarians, and that owing to the local character of the storm, or a chance discharge of lightning, the barbarians suffered more than their opponents. We may well question whether the philosophical emperor himself put any other interpretation than this upon the incident. But, on the other hand, we need not doubt that the major part of his soldiers would very readily accept such an explanation as that given by Dion Cassius, just as most readers of a few centuries later would accept the explanation of Xiphilinus. It is well to bear this thought in mind in considering the static period of science upon which we are entering. We shall perhaps best understand this period, and its seeming retrogressions, if we suppose that the average man of the Middle Ages was no more credulous, no more superstitious, than the average Roman of an earlier period or than the average Greek; though the precise complexion of his credulity had changed under the influence of Oriental ideas, as we have just seen illustrated by the narrative of Xiphilinus.
APPENDIX REFERENCE LIST, NOTES, AND BIBLIOGRAPHIES
CHAPTER I. PREHISTORIC SCIENCE Length of the Prehistoric Period.--It is of course quite impossible to reduce the prehistoric period to any definite number of years. There are, however, numerous bits of evidence that enable an anthropologist to make rough estimates as to the relative lengths of the different periods into which prehistoric time is divided. Gabriel de Mortillet, one of the most industrious students of prehistoric archaeology, ventured to give a tentative estimate as to the numbers of years involved in each period. He of course claimed for this nothing more than the value of a scientific guess. It is, however, a guess based on a very careful study of all data at present available. Mortillet divides the prehistoric period, as a whole, into four epochs. The first of these is the preglacial, which he estimates as comprising seventy-eight thousand years; the second is the glacial, covering one hundred thousand years; then follows what he terms the Solutreen, which numbers eleven thousand years; and, finally, the Magdalenien, comprising thirty-three thousand years. This gives, for the prehistoric period proper, a term of about two hundred and twenty-two thousand years. Add to this perhaps twelve thousand years ushering in the civilization of Egypt, and the six thousand years of stable, sure chronology of the historical period, and we have something like two hundred and thirty thousand or two hundred and forty thousand years as the age of man. "These figures," says Mortillet, "are certainly not exaggerated. It is even probable that they are below the truth. Constantly new discoveries are being made that tend to remove farther back the date of man's appearance." We see, then, according to this estimate, that about a quarter of a million years have elapsed since man evolved to a state that could properly be called human. This guess is as good as another, and it may advantageously be kept in mind, as it will enable us all along to understand better than we might otherwise be able to do the tremendous force of certain prejudices and preconceptions which recent man inherited from his prehistoric ancestor. Ideas which had passed current as unquestioned truths for one hundred thousand years or so are not easily cast aside. In going back, in imagination, to the beginning of the prehistoric period, we must of course reflect, in accordance with modern ideas on the subject, that there was no year, no millennium even, when it could be said expressly: "This being was hitherto a primate, he is now a man." The transition period must have been enormously long, and the changes from generation to generation, even from century to century, must have been very slight. In speaking of the extent of the age of man this must be borne in mind: it must be recalled that, even if the period were not vague for other reasons, the vagueness of its beginning must make it indeterminate. Bibliographical Notes.--A great mass of literature has been produced in recent years dealing with various phases of the history of prehistoric man. No single work known to the writer deals comprehensively with the scientific attainments of early man; indeed, the subject is usually ignored, except where practical phases of the mechanical arts are in question. But of course any attempt to consider the condition of primitive man talies into account, by inference at least, his knowledge and attainments. Therefore, most works on anthropology, ethnology, and primitive culture may be expected to throw some light on our present subject. Works dealing with the social and mental conditions of existing savages are also of importance, since it is now an accepted belief that the ancestors of civilized races evolved along similar lines and passed through corresponding stages of nascent culture. Herbert Spencer's Descriptive Sociology presents an unequalled mass of facts regarding existing primitive races, but, unfortunately, its inartistic method of arrangement makes it repellent to the general reader. E. B. Tyler's Primitive Culture and Anthropology; Lord Avebury's Prehistoric Times, The Origin of Civilization, and The Primitive Condition of Man; W. Boyd Dawkin's Cave-Hunting and Early Man in Britain; and Edward Clodd's Childhood of the World and Story of Primitive Man are deservedly popular. Paul Topinard's Elements d'Anthropologie Generale is one of the best-known and most comprehensive French works on the technical phases of anthropology; but Mortillet's Le Prehistorique has a more popular interest, owing to its chapters on primitive industries, though this work also contains much that is rather technical. Among periodicals, the Revue de l'Ecole d'Anthropologie de Paris, published by the professors, treats of all phases of anthropology, and the American Anthropologist, edited by F. W. Hodge for the American Anthropological Association, and intended as "a medium of communication between students of all branches of anthropology," contains much that is of interest from the present stand-point. The last-named journal devotes a good deal of space to Indian languages.
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