CH. XXIII.

DEVELOPMENT OF SCIENCE.

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CHAPTER XXIII.

SCIENCE OF THE EIGHTEENTH CENTURY.

Great spread of Science in the Eighteenth Century-Advance of the Sciences relating to Living Beings-Foundation of Leyden University in 1574-Boerhaave, Professor of Medicine at Leyden, 1701Foundation of Organic Chemistry by Boerhaave-Influence of Boerhaave upon the study of Medicine-Belief of the Alchemists in 'Vital Fluids'-Boerhaave's Experiments on the Juices of Plants Dr. Hales' Experiments on Plants-Boerhaave's Analyses of Milk, Blood, &c.-Great popularity of his Chemical Lectures.

We have now arrived at the beginning of the eighteenth century, only 175 years before our own day, when the different sciences which we have been tracing in their rise, like little rills on the mountain sides, were beginning to swell out into mighty streams, widening and spreading so rapidly that it is in vain we strain our eyes to try and watch them all. The time had now come when any man who wished to be a discoverer was obliged to devote his whole life to one branch of science, following it out in all its intricate windings. And so we find that about this time each science begins to have a complete history of its own, with its own eminent men, and its peculiar language growing more and more technical so as scarcely to be understood by ordinary readers.

For this reason most general histories of Science stop at this point and refer their readers to special works on the different sciences. I do not, however, propose to do this;

for though I must warn you again more strongly than ever that I can only give you little glimpses of the work that was being done, still I think that if we struggle on through the increasing mass of knowledge and gather up a fragment here and there, you will gain a general idea of the progress of science, and be able to read more advanced scientific books with much greater interest, even though you may have learnt very little of any one science.

Astronomy, Physics, and to a certain extent Chemistry; had made such a start at the end of the seventeenth century that it was a great many years before those men who came after Newton, Halley, Huyghens, and Stahl, had mastered the new discoveries sufficiently to progress any further. Therefore we find that it was not in these sciences that most advance was made in the beginning of the eighteenth century, but in those which relate to living beings, and which are all included under the head of Biology, or the science of life. Medicine, Anatomy, and Physiology were the branches which grew most rapidly about this time; and the five great men whose names stand out most conspicuously are Boerhaave, Haller, John Hunter, Bonnet, and Spallanzani: Boerhaave, as the founder of the study of organic chemistry, Haller and Hunter as the fathers of comparative anatomy, and Bonnet and Spallanzani as the discoverers of some very remarkable facts in physiology. We will take these subjects in regular order, and try to understand something of the work which was done in them.

Medical School of Leyden.-Foundation of Organic Chemistry by Boerhaave, 1701.-On the coast of Holland, just where the Rhine empties itself by a number of small channels into the German Ocean, stands the city of Leyden, which became famous in the year 1574, on account of a

CH. XXIII.

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siege of four months which the starving inhabitants endured with the utmost heroism, when the Protestant Netherlanders were struggling for life and liberty against Philip II. of Spain. The Dutchmen were successful at last and drove out the Spanish army, by cutting away the dykes and letting the sea swallow up their beautiful pastures, their neat villages, and their fruitful orchards; and as a reward for their devotion to the cause, William of Orange founded the University of Leyden, which afterwards became very celebrated.

Hermann Boerhaave, of whose work we are now going to speak, was a Professor of Medicine in this University about a hundred years after its commencement. The son of a Dutch clergyman, he was born in 1668 at Vorhout, one of those same small Dutch villages near Leyden which had been for days under the sea in 1574. His father intended him for the church; but the young student, having been accused of holding false opinions, was only too glad to give up this profession and study medicine, in which he delighted. He was so successful that in 1701 he was made Lecturer of Medicine in the University, and a few years later the Professorships of Chemistry and Botany were also given to him. From that time the Medical School of Leyden became famous all over the world. Students flocked to it from all quarters, and most of the best medical men of Europe were pupils of Boerhaave. This was due chiefly, of course, to his wonderful medical knowledge and his skill as a lecturer; but his popularity was greatly increased by his enthusiasm, kindly temper, and the great interest which he took in the success of his pupils. He was always ready to help others and to give them credit for the work they had done, and it is said that even his enemies could not resist his constant and uniform kind

ness and good-temper. He loved his science too well to hinder its progress by angry disputes; and by imparting this spirit to his pupils he did almost as much for the spread of medical science as by the facts which he taught them.

But besides his influence upon medicine in general there was one particular study which Boerhaave may be said to have founded; this was the chemistry of living substances, or organic chemistry. You will remember that the false science of alchemy had always been much mixed up with chemistry, and the alchemists had some strange mystical notions about 'vital fluids,' which they supposed to exist in animals and plants, and to cause their life and growth. Little by little, however, more correct ideas had grown up in the 16th and 17th centuries about the nature of life. Vesalius, Harvey, Malpighi, Grew, and many others, had gradually described more and more accurately the working of the different organs of a living being, and now Boerhaave went farther, and tried to discover by means of chemistry of what materials these organs themselves are composed.

In the same way that Geber had decomposed or divided up inorganic substances, such as metals and earths, by distillation and sublimation (see p. 44), so Boerhaave proposed to decompose the organic substances of which plants and animals are made, and to discover the materials contained in them. To accomplish this he took a plant, such as rosemary, and putting fresh moist leaves of it into a furnace, heated them gently and drove out all the moisture, which he collected in a separate vessel. When this moisture had cooled down into a liquid he examined it and found that it was made up of water, and of different kinds of oils and essences, according to the plant he had taken. For instance, from rosemary he got an essence with the peculiar