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146 [228] GRAAF
MAYOW [230] Another man also survived transfusion from a sheep. Two other subjects died, however, and Denis was brought into court on the charge of murder. He was acquitted of that and the court decided that Denis was engaged in a legitimate medical effort to help people. Nevertheless (and wisely) they forbade such transfusions in future, and Denis quit the practice of medicine. It was not until the time of Land steiner [973] over two centuries in the future that enough was learned about blood to make transfusion a safe and beneficial procedure. [228] GRAAF, Regnier de Dutch anatomist
Graaf was a student of Sylvius [196] at the University of Leiden and obtained his medical degree from the University of Angers, France, in 1665. One of his fellow students was Swammerdam [224] with whom, in later life, he had disputes over priority. Graaf studied the pancreas and gall bladder and is notable for having col lected the secretions those organs dis charge into the intestine, work he did without a microscope. He is better known, however, for his studies of the reproductive system. In 1668 he described the fine structure of the testicles and in 1673 of the ovary (a word he was the first to use). He de scribed particularly certain little struc tures of the ovary that are still called Graafian follicles in his honor, the name having been given them by Haller [278], As he suspected, he had penetrated to the beginning of life, for within those structures the individual ova or egg cells (not actually to be discovered until the time of Baer [478] a century and a half later) are formed. It was Graaf who first appreciated Leeuwenhoek [221] and introduced his work to the Royal Society. He died, still a young man, of the plague. [229] GREW, Nehemiah English botanist and physician Born: Mancetter Parish, War wickshire, September 1641 Died: London, March 25, 1712 Grew was the only son of a clergyman who placed himself on the side of Parlia ment in the English Civil War. With the return of Charles II, the father lost his income and young Nehemiah’s studies at Cambridge were interrupted. He finally obtained his medical degree at the Uni versity of Leiden in the Netherlands in 1671. He was one of the early members of the Royal Society, serving as secretary in 1677 along with Hooke [223]. He turned his microscope on plants, studying their sexual organs in particu lar, including the pistils (feminine) and stamens (masculine). He observed the individual grains of pollen produced by the latter, which were the equivalent of the sperm cells in the animal world. He wrote a book on the stomachs and intes tines of various creatures in 1681 and, in a lecture before the Royal Society in 1676, was the first to use the term “com parative anatomy.” He also isolated magnesium sulfate from springs at Epsom, Surrey, and this compound has been called “Epsom salts” ever since. [230] MAYOW, John (may'oh) English physiologist Born: Bray, Berkshire, December 1641
Died: London, September 1679 Mayow was educated at Oxford, get ting his bachelor’s degree in 1665 and a doctorate in civil law in 1670. He also studied medicine. He may have worked for a time with Hooke [223]. He was one of the early investigators of gases. He wondered if there might not be some substance held in common by air and by saltpeter, since both en couraged combustion. Mayow compared respiration to com bustion. He suggested that breathing was something like puffing air at a fire; that the blood carried the combustive princi-
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NEWTON [231] pie in air from the lungs to all parts of the body (and to the fetus by way of the placenta). He held that it was this combustive principle that turned dark venous blood into bright arterial blood. He was right, completely right, but he died young and there was no one to take up his theories and carry on. Further more, Stahl’s [241] phlogiston theory took the stage shortly after Mayow’s death and carried all before it—in the wrong direction. It was Lavoisier [334], a century after Mayow’s death, whose work established principles like those of Mayow firmly and permanently. [231] NEWTON, Sir Isaac English scientist and mathemati cian
Born: Woolsthorpe, Lincolnshire, December 25, 1642 Died: London, March 20, 1727 Newton was a Christmas baby by the Julian calendar, but by the Gregorian (which we now use) he was bom on January 4, 1643. Newton, adjudged by many to have been the greatest intellect who ever lived, had an ill-starred youth. He was bom posthumously and prematurely (in the year in which Galileo [166] died) and barely hung on to life. His mother, mar rying again three years later, left the child with his grandparents. (The stepfa ther died while Newton was still a schoolboy.) At school he was a strange boy, interested in constructing mechani cal devices of his own design such as kites, sundials, waterclocks, and so on. He was curious about the world about him, but showed no signs of unusual brightness. He seemed rather slow in his studies until well into his teens and ap parently began to stretch himself only to beat the class bully, who happened to be first in studies as well. In the late 1650s he was taken out of school to help on his mother’s farm, where he was clearly the world’s worst farmer. His uncle, a member of Trinity College at Cambridge, detecting the scholar in the young man, urged that he be sent to Cambridge. In 1660 this was done and in 1665 Newton graduated without particular distinction. The plague hit London and he retired to his mother’s farm to remain out of danger. He had already worked out the binomial theorem in mathematics, a de vice whereby the sum of two functions raised to a power could be expanded into a series of terms according to a simple rule. He was also developing the glim merings of what was later to become the calculus. At his mother’s farm something greater happened. He watched an apple fall to the ground and began to wonder if the same force that pulled the apple downward also held the moon in its grip. Kepler’s [169] laws had now, after half a century, come to be accepted, and New ton used them in his thoughts about the apple and the moon. (The story of the apple has often been thought a myth, but according to Newton’s own words, it is true.)
Now, throughout ancient and medieval times, following the philosophy of Aris totle [29], it had been believed that things earthly and things heavenly obeyed two different sets of natural laws, particularly where motion was con cerned. It was therefore a daring stroke of intuition to conceive that the same force held both moon and apple. Newton theorized that the rate of fall was proportional to the strength of the gravitational force and that this force fell off according to the square of the distance from the center of the earth. (This is the famous “inverse square” law.) In comparing the rate of fall of the apple and the moon, Newton had to dis cover how many times more distant the moon was from the center of the earth than the apple was; in other words, how distant the moon was in terms of the earth’s radius. Newton calculated what the moon’s rate of fall ought to be considering how much weaker earth’s gravity was at the distance of the moon than it was on the surface of the planet. He found his cal culated figure to be only seven eighths of what observation showed it to be in ac tuality, and he was dreadfully disap 148 [231] NEWTON
NEWTON [231] pointed. The discrepancy seemed clearly large enough to make nonsense of his theory.
Some have explained this discrepancy by saying that he was making use of a value of the earth’s radius that was a bit too small. If this was so, then he would calculate earth’s gravity as decreasing with distance a bit too rapidly and he would naturally find that the moon was dropping toward the earth at a rate somewhat less than was actually true. (The dropping of the moon is actually the amount by which its orbit deviates from the straight line. This drop is sufficient to keep it constantly in its orbit but of course not sufficient to make it approach any closer to the earth in the long run.) Others think Newton retreated because he wasn’t sure it was right to calculate the distance from the center of the earth in determining the strength of the gravi tational force. Could the earth’s large globe be treated as though it attracted the moon only from its center? He was not to be reassured on that point until he had worked out the mathematical tech nique of the calculus. This second reason is much more probable, but whatever the reason, New ton put the problem of gravitation to one side for fifteen years. In this same period, 1665-66, Newton conducted startling optical experiments, inspired in that direction, perhaps, when he read a book by Boyle [212] on color. Kepler’s writings on optics had roused his interest. Newton let a ray of light enter a darkened room through a chink in a curtain and pass through a prism of glass onto a screen. The light was re fracted, but different parts of it were refracted to different extents, and the beam that fell on the screen was not merely a broadened spot of light, but a band of consecutive colors in the famil iar order of the rainbow: red, orange, yellow, green, blue, and violet. It might have been thought that these colors were created in the prism, but Newton showed they were present in the white light itself and that white light was only a combination of the colors. He did this by passing the rainbow or “spec trum” through a second prism oriented in reverse to the first, so as to recombine the colors, and, behold, a spot of white light appeared on the screen. If a second prism were placed so that only one band of color fell upon it, that band of color might be broadened or contracted, de pending on the orientation of the prism, but it remained a single color. (Nobody knows exactly why Newton did not report the dark lines that mark the spectrum. Some of his experiments were so conducted that a few of the lines must have been visible. However, he had an assistant run some of the experiments because his own eyes were insufficiently keen, and it may be that the assistant saw the lines but did not consider them sufficiently important to report. At any rate, the discovery, which turned out to be of first importance, had to wait a cen tury and a half for Wollaston [388] and Fraunhofer [450].) Newton’s prism experiments made him famous. In 1667 he returned to Cam bridge and remained there for thirty years. In 1669 his mathematics teacher resigned in his favor and Newton at twenty-seven found himself Lucasian professor of mathematics at Cambridge. (The chair was named after Henry Lucas, who originally provided the money to found the professorship.) A special ruling by the Crown made it un necessary for him to enter the church to hold his job. He only gave about eight lectures (rather poor ones) a year. The rest was research and thought. He was elected to the Royal Society in 1672 and promptly reported his experi ments on light and color to the Society— and as promptly fell afoul of Robert Hooke [223]. Hooke had performed some experi ments with light and prisms but typically had never carried them through to a de cent conclusion and had evolved only half-baked explanations. Nevertheless he attacked Newton at once and maintained a lifelong enmity, clearly founded on jealousy. Even if the greatest intellect that the world has produced, Newton was other wise a rather poor specimen of man. He never married and except for a mild
[231] NEWTON
NEWTON [231] youthful romance never seemed to show any signs of knowing or caring that women exist. He was ridiculously absent- minded and perpetually preoccupied with matters other than his immediate surroundings. He was also extremely sen sitive to criticism and childish in his re action to it. More than once he resolved to publish no more scientific work rather than submit to criticism. In 1673 he even tried to resign from the Royal Society in a fit of petulance and though the resigna tion was not accepted, relations between Newton and the Society remained cold. But Newton’s hatred of criticism did not prevent his being just as contentious as Hooke, though in a less forthright manner. He himself avoided controversy, allowing his friends to bear the brunt of the battle, secretly urging them on, mak ing no move either to protect them or to concede a point. Newton and Leibniz [233] developed the calculus independently and at about the same time. For years this seemed to make no difference and Newton and Leibniz were friendly, but as the fame of both men grew some people substituted “patriotism” for sense. Newton had, as usual, delayed publication, which unnec essarily confused matters. It began to seem a great point as to whether an Englishman or a German had made the discovery and a battle began over which of the two men had stolen the idea from the other. Neither had stolen the idea. Both were first-rate intellects capable of discovering the calculus, especially since this branch of mathematics was very much in the air and had been all but discovered a half century before by Fermat [188], But the battle continued with Newton secretly urging his followers on. The calculus is an indispensable tool in science, but English mathematicians shibbomly continued to utilize Newton’s notation even though that of Leibniz was much more convenient. Thus they cut themselves off from Continental advance in mathematics, and English mathemat ics remained moribund for a century. Newton’s experiments with light and color led him to theorize on the nature of light. Some scientists believed that light, like sound, consisted of a wavelike periodic motion. The ubiquitous Hooke was one and Huygens [215] another. To Newton, however, the fact that light rays moved in straight lines and cast sharp shadows was decisive. Sound, a wave form, worked its way about obstacles so that you could hear around comers. Light does not and you cannot see around comers without a mirror. New ton agreed with Democritus [20], there fore, that light consisted of a stream of particles moving from the luminous ob ject to the eye. The particle theory of light was by no means cut-and-dried. Grimaldi [199] showed that light did bend around obsta cles to a very small extent, and that was hard to explain by particles. Then there was the double refraction of light discov ered by Bartholin [210] and that was even harder to explain. In attempting to handle such matters Newton developed thoughts that were quite sophisticated for the time. Actually, the modern theory of light harks back in some in teresting ways to Newton. Newton’s fol lowers, however, dropped most of the so phistication and revised his theory into a straightforward matter of speeding parti cles. This maintained its sovereignty over the competing wave theory for a cen tury, thanks to Newton’s prestige. (Dur ing the eighteenth and even into the nineteenth century Newton’s name some times carried the deadweight effect that Aristotle’s had in the sixteenth and sev enteenth.) It seemed to Newton that there was no way of preventing spectrum formation when light passed through prisms or lenses. It was for this reason that the refracting telescopes of the time were reaching their limits. It was no use mak ing them larger and expecting greater magnification. Light passing through the lenses cast confusing colored rims about the images of the heavenly bodies and blurred out detail—a phenomenon called “chromatic aberration.” Therefore Newton in 1668 devised a “reflecting telescope” that concentrated light by reflection from a parabolic mir ror, rather than by refraction through a lens. In this he was anticipated in theory
[231] NEWTON
NEWTON [231] but not in practice by James Gregory [226], This reflecting telescope had two ad vantages over the refracting telescope. In Newton’s device, light did not actually pass through glass but was reflected off its surface so that there was no light ab sorption by the glass. Secondly, the use of the mirror eliminated chromatic aber ration. The reflecting telescope was a great advance. Newton’s first telescope was six inches long and one inch in diameter, a mere toy, but it magnified thirty to forty times. He built a larger one, nine inches long and two inches in diameter, in 1671 and demonstrated it to King Charles II, then presented it to the Royal Society, which chose this as the occasion for electing him to membership and which still preserves it. Hooke promptly pre pared one according to Gregory’s some what different design, but it wasn’t nearly as good as Newton’s. The largest modem telescopes are of the reflecting variety. And yet Newton was wrong just the same. It was possible to have a refracting telescope without chromatic aberration and not long after Newton’s death Dollond [273] built one. The 1680s proved the climax of New ton’s life. In 1684 Hooke met Wren [220] and Halley [238] and boasted in his obnoxiously positive way that he had worked out the laws governing the mo tions of the heavenly bodies. Wren was not impressed by Hooke’s explanation and offered a prize for anyone who could solve the problem. Halley, who was a friend of Newton, took the problem to him and asked him how the planets would move if there was a force of attraction between bodies that weakened as the square of the distance. Newton said at once, “In ellipses.” “But how do you know?” “Why, I have calculated it.” And Newton told of his theoretical specula tions during the plague year of 1666. Halley in a frenzy of excitement urged Newton to try again. Now things were different. Newton knew of a better figure on the radius of the earth, worked out by Picard [204], In addition he had worked out the calcu lus to the point where he could calculate that the different parts of a spherical body (with certain conditions of den sity) would attract in such a way that the body as a whole would behave as though all the attraction came out of the center. As he repeated his old calculations, it appeared that this time the answer would come out right. He grew so excited at the possibility (according to one story) that he was forced to stop and let a friend continue for him. Newton began to write a book em bodying all this, completing it in eigh teen months and publishing it in 1687. He called it Philosophiae Naturalis Prin-
ciples of Natural Philosophy”) and it is usually known by the last two words of the title. It was written in Latin and did not appear in English until 1729, forty- two years after its original publication and two years after Newton’s death. It is generally considered the greatest scientific work ever written. Laplace [347] considered it so, for instance, and Laplace was no more inclined to give credit to others than Newton himself was. Despite his invention of the calcu lus, Newton proved the propositions in this book by geometrical reasoning in the old-fashioned way. It was the last great work of science written in the Greek style.
In the book Newton codified Galileo’s findings into the three laws of motion. The first enunciated the principle of iner tia: a body at rest remains at rest and a body in motion remains in motion at a constant velocity as long as outside forces are not involved. This first law of motion confirmed Buridan’s [108] sug gestion of three centuries before and made it no longer necessary to suppose that heavenly bodies moved because an gels or spirits constantly impelled them. They moved because nothing existed in outer space to stop them after the initial impulse. (What produced the initial im pulse is, however, still under discussion nearly three centuries after Newton.) The second law of motion defines a force in terms of mass and acceleration and this was the first clear distinction be Download 17.33 Mb. Do'stlaringiz bilan baham: 
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