Part 4

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, Phœnicians, 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, 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, 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, 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.

Aristotle, Cesalpini, Gesner, and Ray are among the writers who use this word or some synonym.

It has now been made accessible to all readers by the reprint and translation of Mr. A. H. Evans.

Letter of Peter Martyr, Dec. 26, 1515.

The extermination of the red man in North America is the most conspicuous case recorded in history. Australia and Tasmania furnish examples on a smaller scale.

Le Théâtre d'Agriculture, 1600.

PERIOD II.

1661-1740

Characteristics of the Period.

In Western Europe this was a time of consolidation succeeding to one of violent change. Religious wars gave place to dynastic and political wars. In France the tumults of the preceding hundred years sank to rest under the rule of a strong monarchy; order and refinement became the paramount aims of the governing classes; literature, the fine arts, and the sciences were patronised by the Court. Other nations imitated as well as they could the example of France. Learning was still largely classical, but the anti-scholastic revolt, which had first made itself felt three hundred years earlier, steadily gained ground; Descartes, Newton, and Locke were now more influential than the Aristotelians. This was an age of new scientific societies (Royal Society, Academy of Sciences of Paris, Academia Naturæ Curiosorum, etc.).

The Minute Anatomists.

Magnifying glasses are of considerable antiquity. Seneca mentions the use of a glass globe filled with water in making small letters larger and clearer. Roger Bacon (1276) describes crystal lenses which might be used in reading by old men or those whose sight was impaired. As soon as Galileo had constructed his first telescopes, he perceived that a similar instrument might be caused to enlarge minute objects, and made a microscope which revealed the structure of an insect's eye. Within twenty years of this date the working opticians of Holland, Paris, and London sold compound microscopes, which, though cumbrous as well as optically defective, revealed many natural wonders to the curious. Simple lenses, sometimes of high power, came before long to be preferred by working naturalists, and it was with them that all the best work of the seventeenth and eighteenth centuries was done.

The power of the microscope as an instrument of biological research was in some measure revealed by Hooke's Micrographia (1665). Robert Hooke was a man of extraordinary ingenuity and scientific fertility, who took a leading part in the early work of the Royal Society. He opens his book with an account of the simple and the compound microscope of his own day, and then goes on to explain, with the help of large and elaborate engraved plates, the structure of a number of minute objects. The most interesting are: A Foraminiferous shell, snow-crystals, a thin section of cork showing its component cells, moulds, a bit of Flustra, the under side of a nettle-leaf with its epidermic cells and stinging-hairs, the structure of a feather, the foot of a fly, the scales of a moth's wing, the eye of a fly, a gnat-larva, and a flea. The beauty of the plates and the acuteness of some of the explanations are remarkable, but lack of connection between the topics discussed hinders the Micrographia from rising to a very high scientific level.