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CH. XXIII.

ORGANIC CHEMISTRY.

193

scent of rosemary; from the bark of the cinnamon tree, Laurus Camphorum, or Cinnamomum camphorum, he got essence of cinnamon; from its roots, camphor ; and from its leaves an oil with the taste of cloves. Then after he had extracted all the juice from the plant, he burnt the dry remains, to see what would be contained in its ashes after the fire had driven off part of the solid matter as gas, and he found in them a kind of salt, which was also different in different plants. But if he poured hot water on the plant before burning it, he found no salt in the ashes, for it had been dissolved and carried off in the water.

Having now found what substances were in the plant, the next step was to discover where they came from; so he took several specimens of earth in which plants can grow and examined them also; and he found that he could extract from them many of the substances, such as sait, alum, borax, and sulphur, which he had also discovered in the ashes of the plants. It was clear, then, that the plant took these salts out of the earth; and by a number of experiments he went on to prove that they are dissolved by the rain-water which sinks into the earth, and are then sucked up by the plants through their roots and carried up to the leaves, where they are exposed to the air and sunshine, and altered so as to become food for the plant. The other parts which did not come from the soil he concluded must be taken in from the air. These were splendid facts, and curiously enough a celebrated English chemist, Dr. Hales (born 1677, died 1761), made some of the same experiments almost at the same time, which confirmed those of Boerhaave. Hales even went so far as to measure the quantity of water taken in at the roots and given out at the leaves of plants, and he discovered the way in which

plants breathe through the little stomata, or mouths, discovered by Grew (see p. 141).

From the juices of plants Boerhaave next went on to those of animals, and he decomposed in a most beautiful and simple manner milk, blood, bile, and those fluids called chyle and lymph which convey nourishment to the blood. These he compared with the sap, gums, resins, and oils of plants, and showed that animal bodies are made up of altered vegetable matter, just as plants are in their turn composed of matter taken from the soil and the air; and he suggested that by careful experiments it would at last be possible to discover exactly the materials of which all living beings were made.

Boerhaave's analyses of organic substances were very rough and imperfect compared to those which are made now; for you must remember that the four gases, oxygen, hydrogen, nitrogen, and carbonic acid, which we now know are the chief constituents of plants, were not yet discovered. Yet even these rough attempts were so interesting that students crowded round the doors of his lecture-room for hours before the lecture began, to secure admission; and there can be no doubt that his 'Elements of Chemistry,' published in 1732, contained the first steps in the study of the chemistry of living things. Boerhaave was also a celebrated botanist. He died in 1738, and deserves always to be remembered as one of the greatest teachers of the eighteenth century.

Chief Works consulted.-Brewster's 'Encyclopædia '—'Boerhaave;' Cuvier, 'Hist. des Sciences Naturelles ;' Sprengel, 'Hist. de la Médicine,' 1815; Burton's 'Life and Writings of Boerhaave,' 1746; Boer. haave, Elements of Chemistry,' Englished by Dallowe, 1735; Miller's 'Chemistry;' Hales' 'Essays concerning Vegetable Staticks,' 1759.

CH. XXIV.

HALLER-ANATOMIST.

195

CHAPTER XXIV.

SCIENCE OF THE EIGHTEENTH CENTURY (CONTINUED). Childhood of Haller-Foundation of the University of Göttingen in 1736-Haller made Professor of Anatomy-Haller's Anatomical Plates-He discovers the power of Contraction of the Muscles— Rise of Comparative Anatomy-John Hunter's industry in Dissecting and comparing the Structures of different Animals — His Museum and the arrangement of his Collection-Bonnet's Experiments on Plants - Experiments upon Animals by Bonnet and Spallanzani-Regrowth of different parts when cut off-Bonnet's theory of Gradual Development of Plants and Animals-Anatomical Works of Haller-He discovers the power of the Muscles to contract.

Haller, 1708–1777.-Among the pupils of Boerhaave there was one man who became, if possible, even more famous than his master. This was Albert von Haller, son of the Chancellor of Baden, who was born at Berne in 1708, and died in 1777. Haller seems to have been a most extraordinary child; at nine years of age it is said that he knew Latin and Greek, had made a Hebrew and Greek dictionary, a Chaldean grammar, and an historical dictionary! We are not told how good these books were; but how very few boys of nine years old would have been able to write them at all! At seventeen Haller went to Leyden to study under Boerhaave, and under Albinus, a famous anatomist; and at nineteen he was already a doctor of medicine. Having been driven out of Paris because the people were horrified

at his dissecting dead bodies, he went to Berne, where he became professor of anatomy; and in 1736, when George II. of England, who was also Elector of Hanover, founded the University of Göttingen, he went there as professor of anatomy, surgery, and botany, and soon made that University as famous as Boerhaave had made Leyden.

One of his first reforms was to turn the work of his pupils to good account. When medical students are going to pass their last examination they are required to write an essay, or thesis, as it is called, before they can receive their degree of doctor. Haller used always at these times to propose to each one of his students some difficult point in anatomy or physiology, in which he thought new discoveries might be made, and he then drew out a plan for them and showed them how to begin. By this means their essays were often full of new and useful information, and it was a great deal owing to the help of his pupils that Haller was able to publish 180 volumes on science, all more or less valuable.

There was also a very good anatomical theatre at Göttingen, and from dissections made there Haller produced a set of most beautiful anatomical drawings, which he published between 1743 and 1753. You will remember that Vesalius published many fine engravings of parts of the human body (see p. 67), and since his time many others had been made, especially by Haller's master, Albinus. But Vesalius' drawings were coarse, because he had no microscope to help him, and Albinus had only drawn separate parts, such as a muscle, a nerve, or a vein. Haller's plates were the first which showed the different nerves and vessels attached in their right position, and to each plate he added a complete history of the function, or use of the parts drawn. He made these drawings so accurate, and spent so

CH. XXIV.

COMPARATIVE ANATOMY.

197

much time upon each minute structure, that in seventeen years, with all the help he had, he was not able to complete the description of the whole human body.

Haller discovers the Power of the Muscles to Contract. -It was while he was at work at these dissections that he made one great discovery, which you must try to understand. If you clasp your right hand round your left arm, just above the elbow, and then bend your left arm, you will feel the part under your hand swell up and grow hard. The reason of this is that the muscle of your arm, called the biceps, has contracted, or grown shorter and thicker, in the process. of bending your arm. If you open your arm again, the swelling will go down, because the muscle is stretched out. Now before Haller's time it was thought that the muscles could not contract of themselves, but were drawn up by the Haller discovered that this is not so, but that a muscle, if irritated, will draw itself together even when it is quite separated from the nerves, and this has since been proved to be true by a great number of experiments. So that though it is true that our nerves are the cause of our moving, because they excite the muscles and so make them contract, yet the real power of contraction is in the muscle itself.

nerves.

Comparative Anatomy, or the Comparison of Different Structures in Men and Animals.-John Hunter.-Another point in which Haller did good service to science was in comparing the same parts of the body of men and animals, and showing how far they are alike. This study, which is called the study of comparative anatomy, has now become very important, for by examining any organ, such as the heart for example, from the lower animals in which it is very simple, up to man in whom it is complicated, we can

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