Part 16

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But if Pasteur had brought back wealth to ruined countries, if he had returned to Paris happy in the victory he had gained, he had also undergone such fatigues, and had so overstrained himself in the use of the microscope while absorbed in his daily and varied experiments, that in October 1868 he was struck with paralysis of one side. Seeing, as he thought, death approaching, he dictated to his wife a last note on the studies which he had so much at heart. This note was communicated to the Academy of Sciences eight days after this terrible trial.

A soul like his, possessing so great a mastery over the body, ended by triumphing over the affliction. Paralysed on the left side, Pasteur never recovered the use of his limbs. To this day, sixteen years after the attack, he limps like a wounded man. But what stages had this wounded man yet to travel over, what triumphs were yet in store for him!

DECISIVE EXPERIMENTS.

After having dictated this scientific note, which he thought would have been his last, his courage forsook him for a time. 'I regret to die,' he said to his friend, Sainte-Claire Deville, who had hastened to his bedside; 'I should have wished to render more service to my country.' His life was spared, but for several months Pasteur remained entirely paralysed, incapable of the slightest movement. Smitten thus in his full strength at the age of forty-five, he took a sad review of his own state. Even at the height of his attack his mind had always retained its clearness. He had pointed out to the doctor without any faltering of voice the progressive symptoms of the paralysis. Then reproaching himself for having added to the grief of his wife by thus dwelling on the details of his illness, he never allowed another word to escape him about his infirm condition. Sometimes, even when he heard his two assistants, M. Gernez and M. Duclaux, whose devotion to him during those sad days could only be compared to that of his wife, talking to him of future labours, he entered into these thoughts and appeared to add faith to their hopes. He finished by sharing them.

In January 1869, although it was still impossible for him to drag himself about his room, he was so much excited by the contradictions that his system of culture had aroused that he wished to start again for Alais. 'Aided by the method of artificial cultivation,' he remarked, 'we shall soon annihilate these latest oppositions. There is here both a scientific principle and an element of national wealth.'

His wish could not be opposed, but a terrible and anxious journey it was! At some leagues from Alais, at a place called Saint Hippolyte-du-Fort, where the earliest experiments were made, Pasteur stopped. He installed himself--we might rather say he encamped--with his family and his assistants, in a more than humble lodging, one of those miserable, cold, paved houses of the rural districts. Seated in his arm-chair, Pasteur directed the experiments, and verified the observations which he had made the year before. Each of his predictions as to the destiny of the different groups of worms was fulfilled to the smallest detail. In the following spring he left for Alais, where he followed in all their phases, from the egg up to the cocoon, the cultivations there undertaken, and he had the happiness of proving once more the certainty of his method.

But opposition still continued. The French Government, shaken by the violence and tenacity of the opponents, hesitated to decide upon this process of culture. The Emperor interposed; he instructed Marshal Vaillant to propose to Pasteur to go into Austria to the Villa Vicentina, which belonged to the Prince Imperial. For ten years the silk harvest at this place had not sufficed to pay the cost of eggs. Pasteur accepted with joy the prospect of a great decisive experiment. He traversed France and Italy, reclining in a railway carriage or in an arm-chair, and at last arrived at the Imperial villa near Trieste. Pasteur succeeded in a marvellous manner. The sale of the cocoons gave to the villa a net profit of twenty-six million francs. The Emperor, impressed with the practical value of the system, nominated Pasteur a Senator, in the month of July 1870. But this nomination, like so many other things, was swept away before it had time to appear in the 'Journal Officiel.' Pasteur, however, cared little for the title of Senator. He returned to France on the eve of the declaration of war.

A patriot to the heart's core, he learned with poignant grief the news of his country's disasters. The bulletins of defeat, which succeeded each other with mournful monotony, threw him into deep despair. For the first time in his life he had not the strength to work. He lived at his little house in Arbois as one completely vanquished. Those who went into his room found him often bathed in tears. On January 18, 1871, he wrote, to the Dean of the Academy of Medicine at the University of Bonn, a letter in which all his grief and all his pride as a Frenchman were displayed, requesting him to withdraw the diploma of German doctor which the Faculty of Medicine of the University had conferred upon him in 1868. Whilst he wrote this letter, which was a cry of patriotism, his son, enrolled as a volunteer, though hardly eighteen years of age, was gallantly doing his duty in the Army of the East.

STUDIES ON BEER.

The war was over. Little by little the life of the country was resumed, and with returning hope the desire and necessity for renewed work. After two years of infirmity, Pasteur at length began to feel the recovery of health. It was like a slow and gentle renewal of all things. He wished to return as soon as possible to his laboratory in Paris to put into execution projects of experiments which had long been working in his brain. At the moment when he was preparing to start, the rebellion of the Commune broke out. M. Duclaux, who had become Professor of the Faculty of Sciences in Clermont-Ferrand, offered the use of his laboratory to his old master. Pasteur accepted it. Eager to commence an investigation which would bring him again to the study of fermentation, he attacked the diseases of beer. But it was not only for the purpose of creating a new link between these researches and his former ones that he occupied himself with this subject, he was also influenced by a somewhat patriotic idea. He dreamt of success in an industry in which Germany is superior to France. He hoped by means of scientific principles, by which commerce would largely profit, to succeed in making for French beer a reputation equal, if not superior, to that of Germany.

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Beer is much more liable to contract diseases than wine. It may be said that while old wine is often to be found, there is no such thing as old beer. It is consumed as fast as it is made. Less acid and less alcoholic than wine, beer is more laden with gummy and saccharine matters, which expose it to rapid changes. Thus the trade in this beverage is constantly struggling with the difficulties of its preservation.

The manufacture of beer is simple. It is extracted from germinated barley, or malt, an infusion of which is made and gradually heated to the boiling point. It is then flavoured by hops. When the infusion of malt and hops, which is called 'wort,' is completed, it is subjected to a cooling process, and drawn off into tuns and barrels. It is then that alcoholic fermentation sets in. The cooling ought to be performed rapidly. While the wort is at a high temperature there is nothing to fear, it remains sound; but under 70° Centigrade, and particularly between 25° and 35°, it is easily attacked by injurious ferments--acetic, lactic, or butyric. After the wort is cooled, a little of the yeast proceeding from a former fermentation is added to it, in order that the whole mass of the wort should be invaded as soon as possible after its cooling by the alcoholic ferment alone--the only one, properly speaking, which can produce beer. If this wort were treated in the same way as the must of the grape, if it were abandoned to fermentation without yeast--to so-called spontaneous fermentation--this would hardly ever be purely alcoholic, as in the must of grapes, which is protected by its acidity. Most frequently, instead of beer, an acid or putrid liquid would be obtained. Divers fermentations would simultaneously take place in it. When the wort has fermented and the beer is made, there is still the fear of its rapid deterioration, which necessitates its being quickly consumed. This condition is sometimes disastrous to those employed in the beer trade; and the improvements in the manufacture of beer which have been made during the last forty years have all had for their object the removal of this necessity for the daily production, so to speak, of an article of which the consumption is liable to constant variations.

Formerly only one kind of beer was known, the beer of high fermentation. The wort, after having undergone cooling in the troughs, is collected in a large open vat at a temperature of 20°, and yeast is added to it. When the fermentation begins to show itself on the surface of the liquid, by the formation of a light white froth, the wort is transferred to a series of small barrels, which are placed in cellars or store-rooms, kept at a temperature of from 18° to 20° Centigrade. The activity of the fermentation soon causes a foam to rise, which becomes more and more thick and viscous. This is owing to the abundance of yeast which it contains. This yeast, collected in a large trough placed under the casks, is gathered up for future operations. The fermentation lasts for three or four days, then the beer is made and has become clear; the bungs are fixed in the barrels, and they are sent direct to the retail dealer or to the consumer. During the transit, a certain quantity of yeast, fallen to the bottom of the casks, thickens the beer, but a few days of repose suffice to make it again clear and fit to drink, or to be bottled.

This system of 'high' fermentation (so called because it begins at a temperature of 18° to 20°, and is raised one or two degrees higher by the act of fermentation itself) is very commonly practised in the north of France, and to a greater extent in the breweries of England. Ale, pale ale, bitter beer, are all beers from high fermentation.

The 'low' fermentation, which is almost exclusively employed in Germany, and which is spreading more and more in France, consists in a slow fermentation, at low temperature, during which the yeast settles at the bottom of the tubs and casks. The wort, after it has been cooled, is passed into open wooden tuns, and the working of the yeast takes place at a temperature of about 6° Centigrade. This temperature is maintained by means of floats, in the form of cones or cylinders, thrown into the fermenting tuns and kept filled with ice. The fermentation lasts for ten, fifteen, and even twenty days. When the beer is drawn off, the yeast is collected from the bottom of the fermenting tuns. This kind of beer, which is sometimes called German beer, sometimes Strasburg beer, is generally much more esteemed than the other, but it requires certain expensive, or at least inconvenient, conditions. There must be ice-caves, where the temperature is maintained all the year round at a few degrees only above zero. This makes it necessary to have enormous piles of ice. It has been calculated that for one single hectolitre of good beer, from the beginning of the cooling of the wort until the time when it is fit for sale, 100 kilogrammes of ice are required. The 'low' beer, called also bière de garde, beer for keeping, is principally manufactured in winter, and is preserved in ice-caves until the summer.

It is not only the taste of the consumers which has favoured the manufacture of beer of low fermentation everywhere except in England; it is also the advantage this beer possesses in being much less liable to deterioration than the other. By employing ice, the brewer may manufacture in winter, or in the beginning of spring, and thus place himself in a position to meet the demands of consumption without fear of seeing his beer attacked by disease.

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All the diseases of beer, as Pasteur has shown, are caused exclusively by the development of little microscopic fungi, or organised ferments, the germs of which are brought by the dust constantly floating in the air, or which gets mixed with the original substances used in the manufacture. 'By the expression diseases of wort and of beer, I mean,' said Pasteur, 'those serious alterations which affect the quality of these liquids so as to render them disagreeable to the taste, especially when they have been kept for some time, and which cause the beer to be described as sharp, sourish, turned, ropy, putrid.' The wort of beer, after it has been raised to the boiling heat, may, as Pasteur's experiments testify, be preserved indefinitely, even in the highest atmospheric temperatures, when in contact with air free from the germs of the lower microscopic organisms. The must, leavened by the addition of pure yeast, kept free from foreign organisms, contains nothing but the alcoholic ferment, and undergoes no other changes than those due to the action of the oxygen, which does not give rise to acidity, putridity, or bitterness. Since the causes of deterioration are the same in beer as in wine, would it not appear as if the action of heat must be the best preservative? But beer is a drink necessarily charged with carbonic acid, and the application of heat to considerable masses of the liquid would expel this gas. It would be a very complicated business to attempt to preserve this gas, or to introduce it afresh after it had been expelled. This difficulty does not arise when the beer is bottled. At a temperature of 50° to 55°, the process of heating not only cannot take away from the beer all its carbonic acid, but it does not prevent the secondary fermentation from taking place to a certain extent, and this allows of the beer being heated immediately after it is put into bottles. This heating of the beer is practised on a large scale in Europe and in America. In honour of Pasteur the process is called Pasteurisation, and the beer Pasteurised beer.

But Pasteur was not content with simply destroying the ferments of these diseases, he wished above all to prevent their introduction. At the moment when the wort is raised to the boiling-point, when the germs of disease are destroyed by the heat, if the cooling of the wort is effected in contact with both air and yeast free from exterior germs, the beer may be made under conditions of exceptional purity. Some brewers, taking for their basis Pasteur's principles, constructed an apparatus which enabled them to protect the wort while it was cooling from the organisms of the air, and to ferment this wort with a leaven as pure as possible. At the Exhibition of Amsterdam there might be seen bottles half full, containing a perfectly clear beer, which had been tapped from the time of opening of the Exhibition. This was French beer, manufactured according to Pasteur's principles, by a great brewer of Marseilles, M. Velten. The happy effect of these studies is universally recognised. At Copenhagen, M. Jacobsen has had a bust of Pasteur, by Paul Dubois, placed in the salle d'honneur of his celebrated laboratory.

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In terminating his Studies on Beer, Pasteur recalled to mind the principles which for twenty years had directed his labours, the resources and applications of which appeared to him unlimited. 'The etiology of contagious diseases,' he wrote with a scientific certainty of conviction, 'is on the eve of having unexpected light shed upon it.'

VIRULENT DISEASES.

SPLENIC FEVER (CHARBON)--SEPTICÆMIA.

'He that thoroughly understands the nature of ferments and fermentations,' said the physicist Robert Boyle, 'shall probably be much better able than he that ignores them, to give a fair account of divers phenomena of certain diseases (as well fevers as others), which will perhaps be never properly understood without an insight into the doctrine of fermentations.'

At all times, medical theories, more particularly those which concern the etiology of virulent diseases, have had to encounter the opposition of explanations invented to account for the phenomena of fermentation. When Pasteur in 1856 began his labours on these subjects, the ideas of Liebig were everywhere revived. Like the ferments, so the viruses and processes of disease were considered as the results of atomic motions proper to substances in course of molecular change, and able to communicate themselves to the diverse constituents of the living body.

The researches of Pasteur on the part played by microscopic organisms in fermentation, changed the course of these ideas. The ancient medical theory of parasites and living contagia was revived. A German Professor, Dr. Traube, in 1864, put forward, in one of his clinical lectures, a new doctrine of the ammoniacal fermentation of urine.