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421 [642] PASTEUR
PASTEUR [642] the science of polarimetry in which mea surements of the manner in which the plane of polarized light was twisted could be used to help determine the structure of organic substance, to follow various chemical reactions, and so on. He had associated “optical activity” with asymmetry in crystals, but it also showed up in solution where no crystals could exist and where the substance was sepa rated into individual molecules. The most reasonable conclusion was that asymmetry existed in the molecules themselves. Pasteur lived long enough to see the three-dimensional structure of the carbon bonds worked out by Van’t Hoff [829] and Le Bel [787] and once that was done it was quite easy to show that certain molecules were indeed asymmetric and, like the tartrate crystals, existed in mir ror-image forms. It was the best evidence in favor of the Van’t Hoff-Le Bel the ory that just those compounds that ought to exhibit the twisting effect, according to the theory, did exhibit it in actual fact.
It turned out later that Pasteur was lucky in the manner in which he pre pared the crystals. In order to have the two types of crystal form separately (in stead of in the symmetrical combination that fooled Mitscherlich) the preparation had to be made in just one particular way and Pasteur, by sheer chance, had done it that way and very few have man aged, since, to prepare asymmetric crys tals as large as Pasteur’s. However, as Pasteur himself later said, “Chance favors the prepared mind.” Pasteur’s achievement made him fa mous. He obtained a succession of professorial appointments and was made a member of the Legion of Honor. Yet great as his achievement in chemistry had been, it was to be dwarfed by his ac complishments in biology and medicine. In 1854. still in his early thirties, the erstwhile indifferent student became dean of the Faculty of Sciences at the University of Lille; but he was rejected for membership in the Academy of Sci ences in 1857. At Lille, he became interested in the problems of France’s important wine in dustry. Wine and beer often went sour as they aged and millions of francs were lost as a result. Wasn’t there some chem ical that could be added to prevent this? In 1856 a Lille industrialist turned to the famous young chemist and put the prob lem to him. Pasteur agreed to tackle the matter and turned to the microscope. He found almost at once that when wine and beer aged properly, the liquid contains little spherical globules of yeast cells. When wine and beer turn sour, the yeast cells are elongated. Clearly there are two types of yeast, one of which produces al cohol (good) and the other lactic acid (bad). Pasteur was the first to show definitely that fermentation does not re quire oxygen, but that it nevertheless in volves living organisms and that it is nec essary to supply the correct organism to provide the correct type of fermentation. Here he won out in a long controversy with Liebig [532], who insisted that fer mentation was a purely chemical phe nomenon that did not involve living or ganisms. Pasteur pointed out that the lactic acid yeast must not be allowed to remain in the fermenting wine. In the early 1860s he worked out the remedy. Once the wine or beer is formed, it must be heated gently at about 120°F. That would kill any yeast still left, including the wrong ones that would continue to do their souring work while the wine was aging. After the heating, the wine, if stoppered, would not sour. The vintners were horrified at the thought of heating wine. Pasteur heated some samples, left others unheated, and told the vintners to wait a few months. When the heated samples were opened they were all fine. A number of the unheated ones had soured. Ever since, gentle heating, intended to kill undesirable microscopic organisms, has been termed pasteurization. We are most familiar with the pasteurization of milk.
Pasteur’s interest in small yeast cells brought him to the study of how micro scopic life arose. This was a knotty prob lem indeed, and the aged Biot warned Pasteur against becoming involved in it. 4 2 2
[642] PASTEUR
PASTEUR [642] Berzelius [425] had believed in sponta neous generation and in 1858 there had been reports once more of experiments tending to show that life arose sponta neously out of dead matter. This ran counter to the experiments a century earlier of Spallanzani [302]. Vitalists, however, for example Haeckel [707], maintained that Spallanzani, by heating the air above his broth, had destroyed some vital principle in it. Pasteur was a very religious man and there was a certain religious value in disproving the doctrine of spontaneous generation, for it left the matter of cre ation of life in the hands of God. Pas teur was impelled, therefore, to devise an experiment in which air was not heated and yet life did not arise from nonlife. (Pasteur’s religious feelings also led him to reject Darwin’s [554] theory of evolu tion by natural selection.) Pasteur, like Tyndall [626], showed that the dust in air included spores of living organisms and that by introducing dust into nutrient broths he could cause the broth to swarm with organisms. It was next necessary to show that the broth would not develop organisms if dust were kept out. In 1860 he boiled meat extract and left it exposed to air, but only by way of a long, narrow neck bent down, then up. Although unheated air could thus freely penetrate into the flask, any dust particles settled to the bottom curve of the neck and did not enter the flask. The meat extract did not spoil. No decay took place. No organ isms developed. And there was no ques tion now of heated air or of a destroyed vital principle. Pasteur announced his re sults at a gala meeting at the Sorbonne on April 9, 1864, with the leading social and literary luminaries of Paris in atten dance. Biot, alas, had not lived to see the triumph, but a committee of scientists, including Pasteur’s old teacher, Dumas, studied these experiments and found them decisive. They showed the way to the proper techniques for sterilizing nu trient cultures and thus aided the bur geoning science of bacteriology enor mously.
Once and for all, Pasteur had dis proved the doctrine of spontaneous gen eration in the form in which it had been upheld through the nineteenth century. However, the question, in more sophis ticated form, was to arise again in the twentieth century. By now Pasteur was the miracle man of France and had even been admitted into the Academy of Sciences. When, therefore, in 1862, the silk industry in the south was dealt a staggering blow by a disease that was killing the silkworms, the call went out for Pasteur, no one but Pasteur. His old teacher Dumas prodded him to take on the task. “But I never worked with silkworms,” said Pasteur. “So much the better,” said Dumas. In 1865, then, Pasteur traveled south with his microscope. He located a tiny parasite infesting silkworms and the mul berry leaves that were fed to them. Pas teur’s solution was drastic, but rational. All infested worms and infected food must be destroyed. A new beginning must be made with healthy worms and the disease would be wiped out. His advice was followed and it worked. The silk industry was saved. This turned Pasteur’s interest to com municable diseases and he attended the lectures given by Bernard [578]. He began to feel that disease was communi cable in the first place (something the old Greek physicians had not been will ing to allow) and that, disease was com municable because tiny organisms caused it and spread from individual to individ ual. The communication might be by ac tual bodily contact, by the sprayed drop lets of mucus in a sneeze, by infected excreta, and so on. This “germ theory of disease” of Pas teur’s was probably the greatest single medical discovery of all time, for only through an understanding of the nature of infectious disease and the manner of its communication could it be brought under control. Prior to Pasteur’s time, men such as Henle [557] had had the same notion but without the necessary backing of observation and experiment. Others, such as Semmelweiss [607], fought disease successfully by chemical disinfection but did not realize that the reason for the success was that dan-
[642] PASTEUR
PASTEUR [642] gerous germs were being destroyed. For that reason their advances were abortive. After Pasteur’s fermentation experiments and his observations of silkworm disease, Lister [672] was able to introduce chemi cal disinfection with Pasteur’s germ theory as rationale and this time the technique slowly emerged victorious. With the emergence of the germ theory, moreover, biologists began to turn their attention to bacteria in ear nest, Cohn [675] pointing the way. There was almost a tendency to overdo things in the bacteriological enthusiasm that swept the field, but men such as Leuck- art [640] were showing that there were other types of parasites, too. Pasteur himself was almost defeated by circumstance at that time. He had a paralytic stroke in 1868 and for a while was in danger of death. Shortly after, France went to war with Prussia, and Pasteur (almost fifty and still somewhat paralyzed) tried to volunteer for service. Gently Pasteur was conducted home and told to attend to his microscope. All he could do was to return the honorary medical degree he had received from the Prussian University of Bonn. The experience of that disastrous war (in which France was calamitously de feated) impressed Pasteur with the dan gerous conditions in military hospitals. He brought all his prestige to bear on doctors (which was difficult to do, for he had no medical degree and therefore no union card in their business), forcing them to boil their instruments and steam their bandages in order to kill germs and prevent death by infection. The results were overwhelmingly beneficial, and in 1873 Pasteur was made a member of the French Academy of Medicine. He was still without a med ical degree but there was a growing sus picion (and a firm conviction nowadays) that he was the greatest “physician” of all time. Pasteur, with his new medical prestige, turned his attention to anthrax, a deadly disease that ravaged herds of domestic animals. Some doctors denied that any germ was involved in this disease, but Koch [767] claimed to have detected the germs responsible in 1876. Pasteur used his microscope and confirmed Koch, showing not only that the germs existed but also that they were sometimes pres ent as heat-resistant spores that could survive long periods in the ground. The very soil trodden by an infected herd could cause healthy animals to sicken thereafter. Pasteur’s solution was the same as in the case of the silkworm dis ease. Kill the infected animals, burn their bodies, bury them deep. Now he went further. An animal that survived an attack of anthrax was im mune thereafter. Half a century before, Jenner [348] had forced immunity to a dangerous disease by inoculation with a mild version of the disease. Unfortu nately, there was no mild version of anthrax, so Pasteur made his own. By heating the preparation of anthrax germs he destroyed their virulence, yet found they were capable of bringing about the immune response of the original germs. Thus he could safely establish immunity. In 1881 he carried through a dramatic experiment. Some sheep were inoculated with his “attenuated” germs; others were not. After a time all the sheep were inoculated with deadly anthrax germs. Every sheep that had not been treated with attenuated germs caught anthrax and died. Every sheep that had been treated with attenuated germs was not affected by anthrax at all. Pasteur recognized his debt to Jenner by referring to the new type of inocula tion as “vaccination” even though in this case the disease vaccinia was not in volved. Similar methods were established by Pasteur in the fight against chicken chol era and against rabies (hydrophobia), the disease caused by the bite of a mad dog. Pasteur showed that an attenuated germ could be manufactured by passing a rabies infection through different spe cies of animals until its virulence had abated. He was puzzled in this investi gation by not being able to locate the ac tual germ. This did not shake his faith in the germ theory, however. He suggested that the germ was too small to be seen in the microscope. In this he was correct, 4 2 4
[643] WALLACE
WALLACE [643] and this observation foreshadowed the study of viruses that Stanley [1282] was to bring to a climax a half century later. Pasteur in 1885 made the first use of his attenuated rabies preparations to pre vent a case of rabies in a boy badly mauled and bitten by a mad dog. The treatment worked and was the most dra matic climax of a most dramatic life. In 1888 the Pasteur Institute was es tablished with the help of donations from all over the world, including grants from the governments of Russia, Turkey, and Brazil. Its purpose was to treat cases of rabies, and it has now become one of the most famous centers of biological research in the world. (The boy whose life Pasteur had saved from rabies was Joseph Meister, and half a century later he came to a tragic end. He had been made gatekeeper of the Pasteur Institute. In 1940 France was again disastrously defeated, this time by Nazi Germany. The invading Nazis, out of curiosity, ordered Meister to open Pasteur’s crypt. Rather than do so, poor Meister killed himself.) Pasteur died at the height of his glory, recognized both in his lifetime and ever since as one of the greatest scientists in history. In biology it is doubtful that anyone but Aristotle [29] and Darwin can be mentioned in the same breath with him. [643] WALLACE, Alfred Russel English naturalist
January 8, 1823 Died: Broadstone, Dorset, No vember 7, 1913 Wallace, the eighth of nine children of a poor family, had a life that otherwise paralleled that of Darwin [554] in pecu liar fashion. Like Darwin he spent his youth fumbling for a profession, trying surveying and architecture at first. Like Darwin he found his opportunity at last as a naturalist, on a ship sailing off on a voyage of scientific exploration. In 1848 he traveled to the Amazon basin and on his return he too wrote a book about his travels that brought him to the notice of the learned world, even though the ship burned on its return voyage so that many of the records were lost. In 1854 he sailed to the Malay penin sula and the East Indian islands where he collected over 125,000 specimens. There he was struck by the sharp difference between the animal species of Asia and Australia. In later life, writing on this subject, he drew a line separating the lands in which these species occur. The line (still called Wallace’s Line) fol lowed a deep-water channel that ran be tween the large islands of Borneo and Celebes and between the smaller islands of Bali and Lombok. Out of this grew the notion of dividing the animal species into large continental and supercontinen tal blocs (something he eventually devel oped in a book published in 1876). It seemed to Wallace that the animals of Australia were more primitive than those of Asia and that the reason they survived was that Australia and the nearby islands had split off from the Asian mainland before the more ad vanced Asian species had developed. Such thoughts led him to speculate on evolution by natural selection. Exactly as in the case of Darwin, these speculations were brought to a head when he hap pened to read Malthus [387]. Wallace was in Borneo at the time, suffering from malaria, and did not spend many years collecting evidence. Instead, he wrote out the theory in two days and sent the manuscript to Darwin for his opinion. (He had no idea Darwin was working on the same theory.) The two shared publication as a result. Wallace returned to England in 1862. In later years Wallace never could bring himself to believe that man had evolved from the lower animals and he tried to differentiate between man’s body and man’s soul. Oddly enough Wallace was also an articulate crusader against vaccination and managed to adopt an other minority opinion by espousing spir itualism. He also supported socialism— and even that most difficult doctrine for so many men to understand, feminism 425 [644] SIEMENS
HUGGINS [646] [644] SIEMENS, Sir William (see'menz) German-British inventor
1823
Died: London, November 19, 1883
Siemens was a member of a German inventing dynasty, of which his elder brother was the founder. Their first financial success came in the field of electrical engineering. Siemens (he was Karl Wilhelm, then) was educated in Germany at Magdeburg and Gottingen, studying under Wohler [515] and Wilhelm Weber [540], among others. He then went to England in 1842 to introduce a process of electroplating he and his brother had designed. He found that the British patent system was more protective than that in Germany and, eventually, he decided to remain in England. He became a naturalized Brit ish subject in 1859 and was elected to the Royal Society in 1862. Siemens labored to increase the efficiency of steam engines and of the conversion of heat to work, generally, in the light of the new outlook in thermo dynamics, resulting from the work of men such as Joule [613]. It occurred to him and to his younger brother, Fried rich, that the heat of the gaseous prod ucts of combustion was being wasted. If they could be led round so as to preheat the incoming gaseous fuel, there could be a large saving in efficiency. Such a “regenerative furnace” was introduced in 1856, and in 1861 Faraday [474] delivered his farewell lecture on the subject. Siemens applied the regener ative furnace to the smelting of steel and achieved unprecedented economy and re liability in what came to be called the open-hearth method. This eventually re placed Bessemer’s [575] process. Siemens also pioneered in the develop ment of the electric locomotive (he opened an electrified railway in Northern Ireland in 1883), in the laying of trans oceanic cables (designing a ship named Faraday for the purpose), and in im provements in the electric generator. In the last year of his life, he was knighted. [645] KRONECKER, Leopold (kroh'- ne-ker) German mathematician Born: Liegnitz, Silesia (now Leg nica, Poland), December, 7, 1823 Died: Berlin, December 29, 1891 Kronecker was the son of a Jewish merchant and ran the family business eventually. He did well enough to retire at thirty and turn to mathematics with the assurance of running no danger of starvation. He was converted to Protes tant Christianity in the last year of his life. He obtained his Ph.D. from the Uni versity of Berlin in 1845, lectured there from 1861, and by 1883 had gained professorial status despite the fact that he had not yet become Christian. He spent most of his professional career try ing to reinterpret all of mathematics in terms of integers alone. This meant try ing to do without the irrational, which had been accepted since the time of Pythagoras [7], let alone the imaginary numbers dealt with by such men as Hamilton [545] and the infinities of Can tor [772]. Kronecker was the author of a much-quoted statement: “God made the integers; all else is the work of man.” On the whole, his conservative stand did not win out, but it did force mathe maticians to deal with their work with greater rigor. It was not easy to do this as Frege [797] was to find out. [646] HUGGINS, Sir William English astronomer Born: London, February 7, 1824 Died: London, May 12, 1910 Huggins, the son of a linen draper, was privately educated. He was inter ested in microscopy in his younger days but when, in 1856, he was able to dis pose of his father’s business, he turned to astronomy. It was a case of looking through lenses either way, but in the case of astronomy, he did not have to experiment with animals, something he did not enjoy. He built a private observatory near Download 17.33 Mb. Do'stlaringiz bilan baham: |
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