CHOLERA, PLAGUE, SMALLPOX, TYPHUS FEVER, AND YELLOW FEVER-Continued. Reports Received from December 30, 1922 to January 5, 1923-Continued. PUBLIC HEALTH REPORTS VOL. 38 JANUARY 19, 1923 PASTEUR AN APPRECIATION No. 3 AN ADDRESS MADE TO THE STAFF OF THE HYGIENIC LABORATORY AT THE CELE- To-day, December 27, 1922, we commemorate the one-hundredth anniversary of the birth of Pasteur. Louis Pasteur's mother came of a long line of plebeian aristocracy, if we may coin the phrase, people noted for their industry, their intense family loyalty, and their sensitive nature. On the father's side we find a great grandfather who, born a serf, worked his way to the purchase of his freedom. The father, under Napoleon, fought his way to a Cross of the Legion of Honor, and, later, when ordered. to surrender his sword to a policeman of the new régime, he fought for, and, in defiance of authority, retained the cherished blade. Of such stuff was Louis Pasteur-fighter, indefatigable worker, intellectual independent, a lover of family and friend. Pasteur's son-in-law, Vallery Radot, who has given us the above facts, has told of the boyhood and early education of this remarkable. man. There is little about this period that is extraordinary. There were times when homesickness almost got the better of a destiny, and other times when the family purse could hardly stand the strain of modest educational requirements. But at last we find Louis, as a student in Paris, privileged to attend the public lectures of the great chemist, Dumas. There, in the halls of the Sorbonne, was born the chemist, Pasteur. Now, by the very nature of things, no biographer can be specific about the events of thought; but we have some evidence that Pasteur found his own problem for himself. The chum of those student days relates that Pasteur perceived, in the very difficulties of the existing crystallography, an opportunity for discovery. To appreciate properly the situation at that time would require our careful examination of the knowledge then existing. Our time. is too short for this, and we shall have to be content with a bold outline. Let us place a book in the path of a train of electromagnetic waves, with the plane of the leaves parallel to the direction of propagation. The electromagnetic waves, vibrating in all planes perpendicular to the line of propagation, meet the leaves of the book. Those waves which are vibrating parallel to the leaves pass on. Those which are vibrating at an angle to the leaves of the book are damped. The issuing wave train now vibrates in one plane; it is polarized. Let us now place a second book beyond the first. The polarized waves are allowed to pass when the leaves are parallel and are shut off when the leaves are crossed to the plane of vibration. In Pasteur's time the generalized theory was not known. But the principle was known in terms of light. Visible light waves are electromagnetic waves; so-called Nicol's prisms of Iceland spar take the places of our books; and we have the polarimeter, an instrument used by Pasteur. Now, certain substances rotate the plane of polarized light. With such a substance absent, let the second nicol of the polarimeter be turned until the light is just shut off. Then introduce the substance between the nicols. The light from the first polarizing nicol is now rotated till it passes the second "analyzing" nicol. Biot had found that one quartz crystal may rotate the polarized light to the right, another to the left. Hoŭy had found that some quartz crystals have a little facet inclined to the right of a plane which otherwise would be a plane of symmetry, while other quartz crystals have the facet inclined to the left. Herschel was the third investigator required to bring these facts together. Now, whereas quartz rotates when crystalized, it does not rotate when amorphous or in solution. On the other hand, certain organie compounds do not rotate as crystals, but do in solution. Here enters Pasteur. Anyone who has examined crystals as they are formed in the laboratory will realize that they seldom take the beautifully complete form pictured diagrammatically in textbooks. Thus, eminent crystallographers are excused for having missed the little facets on crystals of tartrates. Pasteur saw them. Now that we have been shown, we all have seen them. In the manufacture of tartrate there had been found a curious substance identical in chemical composition and chemical properties with ordinary tartrate. It was then call paratartrate. It had been described as having all the physical properties of tartrate, except an inability to rotate polarized light. Pasteur found on the crystals, however, two symmetrical facets instead of the one asymmetric facet of tartrate. Behold the beauty of the correlation: Asymmetry of crystal---rotation of light by solution; Symmetry of crystal---no rotation of light by solution. Then, a disappointment. On recrystallization, the symmetrical paratartrate separated into asymmetrical crystals - correlation appar ently destroyed. But here flashed genius. These new asymmetric crystals were of two kinds-mirror images of one another, like the right and the left hands. "In spite of all that was unexpected in this result," says Pasteur, "I followed, none the less, my idea. I separated with care the right and left handed hemihedral crystals and observed separately their solutions in the polarization apparatus. Then, with no less surprise than joy, I saw that the right-handed ones turned to the right and the left-handed ones turned to the left the plane of polarization." At last the perfect correlation: Symmetry of crystals--no rotation by solution: Right-handed asymmetry of crystals--right-handed rotation by solution; Left-handed asymmetry of crystals -left-handed rotation by solution. But Pasteur did not stop here. Since the crystals did not rotate while the solution did, it was evident that he must ascribe asymmetry to the chemical molecule. There is a left-handed molecule of tartaric acid. There is a right-handed molecule. There is a mixtureparatartaric acid, now called the racemic mixture. Pasteur has built up evidence for asymmetry of chemical molecules where before only asymmetry of crystals had been given considera tion. The time was not ripe for the further elaboration of this view. Organic chemistry had not come into to its own, and ideas on the structure of organic compounds were hazy. But, 20 years later, when our present structural chemistry was established, Van't Hoff', in Holland, and Le Bel, in France, worked out Pasteur's ideas and gave us modern sterochemistry. To cite but one of many instances: We know to-day several sugars containing 6 carbon atoms. They all have identically the same composition and identically the same structure, except for the spatial arrangement of the atoms, the left and right handed arrangement of the groups about the carbon atoms. Theory calls for 16 steroisomers; 16 and 16 only are known. Pasteur's researches upon tartrates had taken him to factories where he saw the destructive action of molds. They interested him. He studied them; and thus was born Pasteur, the mycologist. Few who have felt the thrill of a discovery can escape its dominating influence. Pasteur was no exception. His vision of asymmetric chemical molecules made him see an asymmetric cosmos. The solar system can have a mirror image. Terrestrial magnetism is asymmetric. Life, he said, is dominated by dissymmetrical actions. Pasteur assailed the hopeless task of trying to influence chemical reactions by mechanical rotation and by magnetic fields. Accomplishing nothing, he returned to the chemistry of life and found in molds the instruments which attack one steroisomer and leave the |