Part 13

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.

* * * * *

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.

* * * * *

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.

* * * * *

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.

'For a long period,' he said, 'the mucus of the bladder was regarded as the agent of the alkaline decomposition of urine. It was supposed that, in consequence of the distension produced by the retention of the liquid, the irritated bladder produced a larger quantity of mucus, and this mucus was regarded as the ferment which brought about the decomposition of urea, by an innate chemical force. This opinion (which was that of Liebig) cannot hold its ground in presence of the researches of Pasteur. This investigator has demonstrated, in the most decisive manner, that alkaline fermentation, like alcoholic and acetic fermentation, is produced by living organisms, the pre-existence of which in the liquid is the _sine quâ non_ of the process.' And Dr. Traube, citing some facts which confirmed the doctrine of Pasteur, concluded thus: 'Notwithstanding the long retention of the urine, its alkaline fermentation is not produced by an increased secretion of mucus or of pus; it only begins to develop from the moment when the germs of vibrios find access to the bladder from without.

The opposite doctrines of Liebig and Pasteur are here brought into clear juxtaposition; and thus was their mutual and reciprocal influence established in dealing with the etiology of one of the most serious diseases of the bladder. So far back as 1862, Pasteur, in his memoir on spontaneous generation, had announced, contrary to all the notions then held, that whenever urine becomes ammoniacal, a little microscopic fungus is the cause of this alteration. Later on he established that in affections of the bladder ammoniacal urine was never found without the presence of this fungus; and in order to show how in these studies therapeutic application often runs hand in hand with scientific discovery, Pasteur, having proved, with his assistant, M. Joubert, that boracic acid is antagonistic to the development of the ammoniacal ferment, advised Dr. Guyon, Clinical Professor of Urinary Diseases in the Faculty of Paris, to combat the dangerous ammoniacal fermentation by injection of boracic acid into the bladder. The celebrated surgeon hastened to follow this advice, and with the most happy results. While attributing to Pasteur the honour of this discovery, M. Guyon, in one of his lectures, said:--

'Boracic acid has this immense advantage, that it can be applied in large doses--3 to 4 per cent.--without causing the slightest pain. It has therefore become, in our practice, the agent continually and successfully used for injections. I also have recourse to a solution of boracic acid to produce large evacuations after the operation of breaking up stones in the bladder (lithotrity). I never omit to use this antiseptic agent in operations where breaking up is required, and I never wash the bladders of lithotritised patients with any other substance. I have also had good results from copiously washing the bladders and the wounds of patients on whom lithotomy has been performed with boracic acid. I always finish the operation by prolonged irrigations with a solution of from 3 to 4 per cent.'

It was not only into France and Germany that Pasteur's ideas penetrated; in England, surgery borrowed from Pasteur's researches important therapeutic applications. In 1865 Dr. Lister began in Edinburgh the brilliant series of his triumphs in surgery by the application of his antiseptic method, now universally adopted. In the month of February 1874 in a letter which does honour to the sincerity and modesty of the great English surgeon, he wrote to Pasteur as follows:--

'It gives me pleasure to think that you will read with some interest what I have written about an organism which you were the first to study in your memoir on lactic fermentation. I do not know whether you read the 'British Medical Journal;' if so, you will from time to time have seen accounts of the antiseptic system which for the last nine years I have been trying to bring to perfection. Allow me to take this opportunity of sending you my most cordial thanks, for having, by your brilliant researches, demonstrated to me the truth of the germ theory of putrefaction, thus giving me the only principle which could lead to a happy end the antiseptic system.'

Pasteur followed with lively interest the movement of thought and the successful applications to which his labours had given rise. It was a realisation of the hopes he had ventured to entertain. Already, in 1860, he expressed the wish that he might be able to carry his researches far enough to prepare the way for a profound study of the origin of diseases. And, as he gradually advanced in the discovery of living ferments, he hoped more and more to arrive at the knowledge of the causes of contagious diseases.

Nevertheless, he hesitated long before definitely engaging himself in this direction. 'I am neither doctor nor surgeon,' he used to repeat with modest self-distrust. But the moment came when, notwithstanding all his scruples, he could no longer be content himself to play the part of a simple spectator of the labours started by his studies on fermentation, on spontaneous generation, and on the diseases of wines and beer. The hopes to which his methods gave rise, the eulogies of which they were the object, obliged him to go forward. In February 1876 Tyndall wrote to him thus:--

'In taking up your researches relating to infusorial organisms, I have had occasion to refresh my memory of your labours; they have revived in me all the admiration which I felt on first reading them. It is my intention to follow up these researches until I shall have dissipated every doubt that has been raised as to the unassailable exactitude of your conclusions.

'For the first time in the history of science we are able to entertain the sure and certain hope that, in relation to epidemic diseases, medicine will soon be delivered from empiricism, and placed upon a real scientific basis. When this great day shall come, humanity will recognise that it is to you the greatest part of its gratitude is due.'

Pasteur approached the study of viruses by seeking to penetrate into all the causes of the terrible malady called splenic fever (_charbon_, Germ. _Milzbrand_). Each year this disease decimates the flocks not only in France but in Spain, in Italy, in Russia, where it is called the Siberian plague, and in Egypt, where it is supposed to date back to the ten plagues of Moses. Hungary and Brazil pay it a formidable yearly tribute; and to come back to France, the losses have amounted in certain years to from fifteen to twenty millions of francs. For centuries the cause of this pest has eluded all research; and further, as the malady did not always exhibit the same symptoms, but varied according to the kind of animal that was smitten by it, the disease was supposed to vary with the species that was attacked by it. The splenic fever of the horse was distinct from that of the cow; the splenic fever of horse and cow were again different from that of the sheep. In the latter, splenic fever was called _sang-de-rate_; in the cow, it was _maladie du sang_; in the horse, splenic fever; in man, malignant pustule.

It was not until 1850 that trustworthy data were first collected regarding the nature of the malady, its identity with and difference from other maladies. From 1849 to 1852 a commission of the Medical Association of Eure-et-Loir made a great number of inoculations, applied other tests, and proved that the splenic fever of the sheep is communicable to other sheep, to the horse, to the cow, and to the rabbit; that the splenic fever of the horse is communicable to the horse and to the sheep; that the splenic fever of the cow is communicable to the sheep, to the horse, and to the rabbit. As for the malignant pustule in man, no doubt remained that it must arise from the same cause as splenic fever in animals. What class of men is it that the malignant pustule most frequently attacks? Shepherds, cowherds, cattle breeders, farm servants, dealers in hides, tanners, wool cleaners, knackers, butchers--all who derive their living from domestic animals. In handling contaminated subjects the slightest excoriation or scratch of the skin is sufficient to allow the virus to enter. When others besides the class that we have named become infected, it is because they live in the neighbourhood of herds smitten with splenic fever. There are also certain flies which transport the virus. Suppose one of these flies to have sucked the blood of an animal which has died of splenic fever, a person stung by that fly is forthwith inoculated with the virus.

At the very time (1850) when these first experiments were being made by the Medical Association of the Eure-et-Loir, Dr. Rayer, giving an account in the 'Bulletin de la Société de Biologie de Paris' of the researches he had made, with his colleague, Dr. Davaine, on the contagion of splenic fever, wrote:--'In the blood are found little thread-like bodies about twice the length of a blood corpuscle. These little bodies exhibit no spontaneous motion.'

This is the date of the first observation on the presence of little parasitic bodies in splenic fever, but, strange to say, no attention was paid to these minute filaments. Rayer and Davaine also paid no attention to them. This indifference lasted for thirteen years; it would have lasted longer still, if the parasitic origin of communicable diseases had not been brought before the mind by each new publication of Pasteur's. From 1857 to 1860 it will be remembered that he had demonstrated lactic fermentation, like alcoholic fermentation, to be the work of a living ferment; in 1861 he had discovered that the agent of butyric fermentation consisted of little moving thread-like bodies, of dimensions similar to those of the filaments discovered by Davaine and Rayer in the blood of splenic fever patients; in 1861 he had announced that no ammoniacal urine existed without the presence of a microscopic organism; in 1863 he had established that the bodies of animals in full health are sealed against the introduction of the germs of microscopic organisms; that blood drawn with sufficient precaution from the veins and the arteries, and urine taken direct from the bladder, could be exposed to the contact of pure air without putrefaction, and without the appearance of living thread-like organisms of any kind whatever, mobile or immobile. It was all these facts which in 1863 brought back the attention of Davaine, as he himself has acknowledged, to the observation which he had made in 1850.