Aristotle found himself obliged to rectify the traditional classification of animals in order to remove gross anomalies. When learning decayed the traditional classification came back. Thus the Ortus Sanitatis (first published in 1475, and often reprinted) adopts the division into (1) animals and things which creep on the earth; (2) birds and things which fly; (3) fishes and things which swim. No consistent primary division of plants was proposed by Greek or Roman, nor by anyone else until the seventeenth century A.D.

This conflict of systems should have raised questions concerning the nature of classification and the relative value of characters. Some of the most striking resemblances found among animals and plants are only superficial; others, though far less obvious, are fundamental. Whence this difference? Why should scientific zoology make so little of the place of abode and the mode of locomotion; so much of the mode of reproduction and the nature of the skeleton? The answers were vague, and even the questions were rare and indistinct. But a metaphorical term came into use which was henceforth more and more definitely associated with fundamental, as distinguished from adaptive, likeness. Such likeness was called affinity,[1] though no attempt was made to explain in what sense the term was to be understood. As late as the year 1835 one of the first botanists in Europe (Elias Fries) could say no more about affinity between species than that it was quoddam supernaturale, a supernatural property.

A tolerable outline of a classification of animals was attained much earlier than a tolerable classification of plants. The characters available for the classification of plants are, to begin with, less obvious than those which the zoologist can employ. Moreover, the botanists were restricted to a narrower view of their subject. Zoologists, though they were expected to bestow the best part of their time upon vertebrates, were encouraged to study all animals more or less. Botanists, on the other hand, were practically obliged to concentrate their attention upon the classification of the flowering plants. The physician, herb-collector, and gardener cared nothing about any plants except such as bear flowers and fruit; but of these they expected full descriptions, and were clamorous for a system which would enable even a tyro to make out every species with certainty and ease. The task set before the botanist was comparable in respect of difficulty with the construction of a detailed and completely satisfactory classification of birds, which zoology has never yet been able to produce, while for the sake of this long-unattainable object almost everything else in botany was neglected.

The First English Naturalists.

During the greater part of three centuries (1300 to 1600), while the revival of learning and science was proceeding actively in Italy, France, Switzerland, and the Rhineland, England lagged behind. Humanist studies were indeed pursued with eminent success in the England of Sir Thomas More, but there was little else for national pride to dwell upon. The re-opening of ancient literature, the outpouring of printed books, the Reformation, the new mathematics and astronomy, the new botany and zoology, were mainly the work of foreigners. Before the seventeenth century no Englishman was recognised as the founder of a scientific school.

Passing over Edward Wotton (1492-1555), who recast the zoology of Aristotle with very little effect upon the progress of biology, we may head the list of English naturalists with the name of William Turner (d. 1568), who wrote on the plants and birds of Britain. Turner was a Reformed preacher, who had been the college friend of Ridley and Latimer. Being banished for preaching without licence, he studied medicine and botany in Italy, at Basle and at Cologne. Under Edward VI. he returned to England and was made Dean of Wells, fled again to the Continent on Mary's accession, was re-instated by Elizabeth, was suspended for non-conformity, and died not long after. Turner's herbal (1551-63) cannot be said to have done much for English botany. The arrangement is alphabetical, the properties and virtues of the plants are described out of ancient authors, and most of the figures are borrowed. Still, it was something to have the common plants of England examined by a man who had studied under Luke Ghini, had botanised along the Rhine, and was the pupil, friend, and correspondent of Conrad Gesner, the most learned naturalist in Europe. Turner's History of Birds (Historia Avium) was published in Latin at Cologne in 1544,[2] and is therefore earlier than Belon's book of birds. The history contains here and there among passages culled from the ancients a sprightly description of the feeding or nest-building of some English bird, and furnishes evidence of the breeding in our islands of birds which, like the crane, have long been known to us only as rare visitants. Of the kite Turner says that in the cities of England it used to snatch the meat out of the hands of children. In his day the osprey was better known to Englishmen than they liked, for it emptied their fishponds; anglers used to mix their bait with its fat. Turner shows not a little of that spirit of close observation which in a later and more tranquil age shone forth in Gilbert White.

Dr. John Caius (the name is supposed to be a Latinised form of Kay), the second founder of a great Cambridge college, was physician in succession to Edward VI., Mary, and Elizabeth; in his youth he had studied under Vesalius at Padua. Like Turner he was a friend and correspondent of Gesner, for whom he wrote an account of the dogs of Britain (De Canibus Britannicis, printed in Latin in 1570), which attempts to classify all the breeds, and to give some account of the uses to which each was put. The list contains no bull-dog, pointer, or modern retriever. There is a water-spaniel, however, and dogs had already been trained to retrieve game. The turnspit, which was not a distinct breed (Caius calls it a mongrel), has long been superseded. Curious antiquarian information, such as mention of the weapons formerly used by sportsmen, and obsolete names of dogs, reward the reader of this short tract.

Thomas Moufet wrote (for Gesner again) a book on insects, which incorporated the notes of Penny and Wotton. None of the three lived to see the printed book, which was at last put forth by Sir Thomas Mayerne in 1634. It is uncritical, confused, and illustrated by the rudest possible woodcuts.

John Gerarde's Herbal (1597) and Parkinson's two books of plants are more amusing than valuable. Both authors were guilty of unscrupulous plagiarism, a vice which cannot be atoned for by curious figures and bits of folk-lore, nor even by command of Shakespearean English. Thomas Johnson's edition of Gerarde (1633) is a far better book than the original; Ray called it "Gerarde emaculatus"—i.e., freed from its stains.

The succession of influential English naturalists may be said to begin with Ray, Willughby, and Martin Lister, all of whom belong to the last half of the seventeenth century.

The Rise of Experimental Physiology.

1543 is a memorable year in the history of science. Then appeared the treatise of Copernicus on the Revolutions of the Heavenly Bodies, completed long before, but kept back for fear of the cry of novelty and absurdity which, as he explains in his preface, dull men, ignorant of mathematics, were sure to raise. The aged astronomer, paralysed and dying, was able to hold his book in his hands before he passed away. In the same year Vesalius, a young Belgian anatomist, published his Structure of the Human Body, a volume rich in facts ascertained by dissection. Some of these facts were held to contradict the teaching of Galen. Next year Vesalius was driven by the hostility of the medical profession to burn his manuscripts and relinquish original work; he was not yet thirty years of age.

Galen had taught that there are two sets of vessels in the body (arteries and veins), and that in each set there is an ebb and flow. Knowing nothing of communications between the ultimate branches of the arteries and veins, and shrinking from the supposition that the arteries and veins are entirely separate and distinct, Galen had taught that the blood passes from one set of vessels to the other in the heart. The septum between the ventricles must be porous and allow the blood to soak through. Vesalius did not venture openly to challenge the physiology of Galen, but he significantly admired the "handiwork of the Almighty," which enables the blood to pass from the right to the left ventricle through a dense septum in which the eye can perceive no openings. Fabricius of Acquapendente in 1574 demonstrated the valves of the veins, though he never arrived at a true notion of their action. His celebrated pupil, William Harvey, who had been anticipated on important points by the Spaniard Michael Servetus and Realdo Columbo of Cremona, published in 1628 a clear account, supported by adequate experimental evidence, of the double circulation through the body and the lungs, and of the communications between the arteries and the veins in the tissues—communications which it was reserved for the next generation to demonstrate by the microscope.

Aselli of Cremona rediscovered the lacteals in 1622; they had been known ages before to Erasistratus, but forgotten. Opening the abdomen of a dog, he saw a multitude of fine white threads scattered over the mesentery, and observed that when one of them was pricked a liquid resembling milk gushed out. Further examination showed him that these vessels, like the veins, possess valves which permit flow in one direction only. Pecquet, a French physician, announced in 1651 that the lacteals open into a thoracic duct, which joins the venous system. In 1653 Rudbeck of Upsala described yet another set of vessels, the lymphatics; these again are provided with valves, and open into the thoracic duct, but are filled with a clear liquid.

The effect of these discoveries upon physiology and medicine was very great, but it did not end there; the whole circle of biological students and a still wider circle of men who pursued other sciences were thereby encouraged to follow the experimental path to knowledge. Wallis, in describing the meetings of scientific men held in London in 1645 and following years, mentions the circulation of the blood, the valves in the veins, the lacteals, and the lymphatic vessels among the subjects which had stirred their curiosity; while the naturalist Ray thanked God for permitting him to see the vain philosophy which had pervaded the University in his youth replaced by a new philosophy based upon experiment—a philosophy which had established the weight and spring of the air, invented the telescope and the microscope, and demonstrated the circulation of the blood, the lacteals, and the thoracic duct.

The Natural History of Distant Lands (Sixteenth Century and Earlier).

Travel and commerce had made the ancient world familiar with many products of distant countries. Well-established trade routes kept Europe in communication with Arabia, the Persian Gulf, and India. Egyptians, Phoenicians, and Greeks explored every known sea, and brought to Mediterranean ports a variety of foreign wares. Under the Roman empire strange animals were imported to amuse the populace; silk, pearls, gay plumage, dyes, and drugs to gratify the luxury of the rich.

Long after the fall of the empire foreign trade was kept up along the coasts of the Mediterranean. Constantinople was still a great emporium. Silk was not only imported from the East, but cultivated around Constantinople in the sixth century. The cotton plant, the sugarcane, the orange tree, and the lemon tree gradually spread northward and westward until they became established in Italy, Spain, and the islands of the Mediterranean.

Western Europe had during many centuries little share in this commerce. The large and conspicuous animals of Africa and Asia, such as the elephant, camel, camelopard, ostrich, pelican, parrot, and crocodile, would have passed out of knowledge altogether but for chance mention in the Bible and the Bestiaries. Little was done to supplement native food-plants and drugs by imported products, and the knowledge of foreign vegetation became as indistinct as that of foreign animals.

In the thirteenth century communication between Western Europe and the far East was restored. China was thrown open by the Tartar conquest, and Marco Polo was able to reach the court of Khan Kublai. Pilgrims from the Holy Land brought back information which, however scanty it might be, was eagerly received. One of the earliest printed books (1486) contains the travels of Bernard of Breydenbach, a canon of Mainz, whose narrative is adorned by curious woodcuts, in which we can make out a giraffe and a long-tailed macaque.

The geographical discoveries of the sixteenth century gave men for the first time a fairly complete notion of the planet which they inhabit. Circumnavigators proved that it is really a globe. Maps of the world, wonderfully exact considering the novelty of the information which they embodied, were engraved as early as 1507. The explorers of America busied themselves not only with the preparation of charts, the conquest of Mexico and Peru, the search for gold, and the spread of the true faith, but also with the strange animals and plants which they saw; and the news which they brought back was eagerly received in Europe. Queen Isabella charged Columbus, when he set out for his second voyage, to bring her a collection of bird-skins; but this may be rather a proof of her love of millinery than of her interest in natural history. Pope Leo X. liked to read to his sister and the cardinals the Decades of Peter Martyr Anglerius,[3] in which the productions of the New World are described. The opossum, sloth, and ant-eater, the humming-bird, macaw, and toucan, the boa, monitor, and iguana, were made known for the first time. Potatoes and maize began to be cultivated in the south of Europe, the tomato was a well-known garden plant, the prickly pear was spreading along the shores of the Mediterranean, and tobacco was largely imported. By the end of the seventeenth century Mirabilis and the garden TropÆolum had been brought from Peru, the so-called African marigold from Mexico, and sunflowers from North America. More than a hundred years had still to run before the evening primrose, the passion flower, and the lobelias of America were to become familiar to European gardeners, ipecacuanha and cinchona to European physicians.

Agriculture, Horticulture, and Silk-Culture in the Sixteenth Century.

During the darkest parts of the Middle Ages agriculture and horticulture were regularly practised. Tyranny, the greed of settlers, the inroads of barbarians, private war, and superstition may destroy all that brightens human life, but they hardly ever exterminate the population of large districts,[4] and so long as men live they must till the soil.

The age of Charlemagne was one of cruel hardship to the inhabitants of Western Europe, but the cartularies of the great king show that the improvement of horticulture was a matter of much concern with him. The nobles and the religious houses kept trim gardens, which are delineated in mediÆval paintings. We know less about the state of the peasantry, but it is clear that they ploughed, sowed, reaped, and dug their little gardens, however uncertain the prospect of enjoying the produce of their labour.

The progressive Middle Ages (about 1000 to 1500 A.D.) greatly increased the comfort of the wealthy and alleviated the miseries of the poor. We now hear of countries (England, the Low Countries, the western half of Germany, the northern half of Italy) where freemen cultivated their own land, or grew rich by trade, and these men were not content barely to support life. Under the later Plantagenets the wool-growers of that upland country which stretches from Lincolnshire to the Bristol Channel showed their wealth by building a profusion of manor-houses and beautiful perpendicular churches, many of which still remain. There can be little doubt that they were attentive to the rural industries which are so great a source of comfort and pleasure.

In the sixteenth and seventeenth centuries the Flemings, a laborious and enterprising people, inhabiting a fertile country, excelled the rest of Europe in agriculture and horticulture. L'Obel, himself a Fleming, speaks with pride of the live plants imported into Flanders from Southern Europe, Asia, Africa, and America. By the close of the sixteenth century, or a few years later, the lilac, lavender, marigold, sun-flower, tulip, and crown-imperial, the cucumber and garden rhubarb, besides many improved varieties of native vegetables, were sent out from Flanders to all parts of Western Europe. During many generations English agriculture and horticulture, and not these alone, but English ship-building, navigation, engineering, and commerce as well, looked to the Low Countries as the chief schools of invention and the chief markets from which new products were to be obtained.

Late in the sixteenth century a gentleman of the Vivarais (the modern ArdÈche), named Olivier de Serres, wrote a book on the management of land,[5] which leaves a strong impression of the zeal for improvement which then pervaded Europe. De Serres was above all things intent upon extending silk-culture in France. On this topic he wrote with full knowledge, having reared silkworms for thirty-five years. The King, Henri Quatre, shared his hopes, and gave him practical encouragement. It is well known that a great industry was thus started; by 1780 the annual yield of silk-cocoons in France was valued at near a million sterling, while in 1848 it had risen to four millions. De Serres sought to promote the cultivation of the mulberry tree, not only because its leaves are the food of the silkworm, but because he believed that the fibres of the bast would be serviceable in the manufacture of cordage and cloth. He also tried to revive the ancient practice of hatching eggs by artificial heat. We learn from him that the turkey, recently introduced from Mexico, had already become an important addition to the poultry-yard, while maize from Mexico and beetroot from the Mediterranean coasts were profitable crops. Among the new appliances De Serres mentions artificial meadows, wind and water-mills, cisterns not hewn from stone, and greenhouses.