Part 698

The question of fermentation "had come to present an entirely new aspect through the discovery of Cagniard de la Tour that yeast is really a plant belonging to one of the lowest types of fungi, which grows and reproduces itself in the fermentable fluid, and whose vegetative action is presumably the cause of that fermentation, just as the development of mould in a jam-pot occasions a like change in the upper stratum of the jam, on whose surface, and at whose expense, it lives and reproduces itself. Chemists generally—especially Liebig, who had a fermentation theory of his own—pooh-poohed this idea altogether; maintaining the presence of the yeast-plant to be a mere concomitant, and refusing to believe that it had any real share in the process. But in 1843, Professor Helmholtz, then a young undistinguished man, devised a method of stopping the passage of organic germs from a fermenting into a fermentable liquid, without checking the passage of fluids; and as no fermentation was then set up, he drew the inference that the 'particulate' organic germs, not the soluble material of the yeast, furnish the primum mobile of this change,—a doctrine which, though now universally accepted, had to fight its way for some time against the whole force of chemical authority. A little before Cagniard de la Tour's discovery, a set of investigations had been made by Schulze and Schwann, to determine whether the exclusion of air was absolutely necessary to prevent the appearance of living organisms in decomposing fluids, or whether these fluids might be kept free from animal or vegetable life, by such means as would presumably destroy any germs which the air admitted to them might bring in from without, such as passing it through a red-hot tube or strong sulphuric acid. These experiments, it should be said, had reference rather to the question of 'spontaneous generation,' or 'abiogenesis,' than to the cause of fermentation and decomposition; its object being to determine whether the living things found by the microscope in a decomposing liquid exposed to the air, spring from germs brought by the atmosphere, or are generated 'de novo' in the act of decay—the latter doctrine having then many upholders. But the discovery of the real nature of yeast, and the recognition of the part it plays in alcoholic fermentation, gave an entirely new value to Schulze's and Schwann's results; suggesting that putrefactive and other kinds of decomposition may be really due, not (as formerly supposed) to the action of atmospheric oxygen upon unstable organic compounds, but to a new arrangement of elements brought about by the development of germinal particles deposited from the atmosphere. It was at this point that Pasteur took up the inquiry; and for its subsequent complete working-out, science is mainly indebted to him: for although other investigators—notably Professor Tyndall—have confirmed and extended his conclusions by ingenious variations on his mode of research, they would be the first to acknowledge that all those main positions which have now gained universal acceptance—save on the part of a few obstinate 'irreconcilables'—have been established by Pasteur's own labours. … The first application of these doctrines to the study of disease in the living animal was made in a very important investigation, committed to Pasteur by his old master in chemistry (the eminent and eloquent Dumas), into the nature of the 'pébrine,' which was threatening to extinguish the whole silk culture of France and Italy. … Though it concerned only a humble worm, it laid the foundation of an entirely new system and method of research into the nature and causes of a large class of diseases in man and the higher animals, of which we are now only beginning to see the important issues. Among the most immediately productive of its results, may be accounted the 'antiseptic surgery' of Professor Lister; of which the principle is the careful exclusion of living bacteria and other germs, alike from the natural internal cavities of the body, and from such as are formed by disease, whenever these may be laid open by accident, or may have to be opened surgically. This exclusion is effected by the judicious use of carbolic acid, which kills the germs without doing any mischief to the patient; and the saving of lives, of limbs, and of severe suffering, already brought about by this method, constitutes in itself a glorious triumph alike to the scientific elaborator of the germ-doctrine, and to the scientific surgeon by whom it has been thus applied. A far wider range of study, however, soon opened itself. The revival by Dr. Farr of the doctrine of 'zymosis' (fermentation),—long ago suggested by the sagacity of Robert Boyle, and practically taken up in the middle of the last century by Sir John Pringle (the most scientific physician of his time),—as the expression of the effect produced in the blood by the introduction of a specific poison (such as that of small-pox, measles, scarlatina, cholera, typhus, &c.), had naturally directed the attention of thoughtful men to the question (often previously raised speculatively), whether these specific poisons are not really organic germs, each kind of which, a real 'contagium vivum,' when sown in the circulating fluid, produces a definite 'zymosis' of its own, in the course of which the poison is reproduced with large increase, exactly after the manner of yeast in a fermenting wort. Pasteur's success brought this question to the front, as one not to talk about, but to work at."

_W. B. Carpenter, Disease-Germs (Nineteenth Century, October, 1881)._

ALSO IN: _L. Pasteur, Studies in Fermentation._

_Dr. Duclaux, Fermentation._

MEDICAL SCIENCE: 19th Century. Virchow and Cellular Pathology.

"That really gifted scholar and paragon of industry and attainment, Rudolph Virchow, announced in 1858 a theory known as Modern Vitalism which was borrowed from natural scientific medicine and is distinguished from the vitalism of the previous century in this, that it breaks up the old vital force, which was supposed to be either distributed throughout the entire body, or located in a few organs, into an indefinite number of associate vital forces working harmoniously, and assigns to them all the final elementary principles without microscopic seat. 'Every animal principle has a sum of vital unities, each of which bears all the characteristics of life. {2146} The characteristics and unity of life cannot be found in any determinate point of a higher organism, e. g., in the brain, but only in the definite, ever recurring arrangements of each element present. Hence it results that the composition of a large body amounts to a kind of social arrangement, in which each one of the movements of individual existence is dependent upon the others, but in such a way that each element has a special activity of its own, and that each, although it receives the impulse to its own activity from other parts, still itself performs its own functions.' This it will be seen is nothing but another way of expressing the cell doctrine to which most medical men are now committed, which means that our bodies are built up with cells, and that each cell has a unity and a purpose of its own. Sir Robert Hooke in 1677 discovered plant cells. Schwann discovered animal cells, and Robert Brown discovered cell nuclei, but it remained for Virchow, using the microscope, to supply the gap which had risen between anatomical knowledge and medical theory, that is, to supply a 'cellular pathology,' since which time the cell has assumed the role which the fibre occupied in the theories of the 17th and 18th centuries. Time alone can decide as to the ultimate validity of these views. This theory was from its announcement most enthusiastically received, and so far has responded to nearly all the requirements which have been made of it. Even its author was almost startled with its success. … As a result of Virchow's labors there has arisen in Germany what has been called the medical school of natural sciences of which Virchow is the intellectual father. This school seeks mainly by means of pathological anatomy and microscopy, experimental physiology and pathology, and the other applied sciences, or rather by their methods, to make medicine also an exact science."

_Roswell Park, Lectures on the History of Medicine (in MS.)._

MEDICAL SCIENCE: 19th Century. The development of Bacteriology.

"The traditional expression contagium vivum received a more precise meaning in 1840 from Henle, who in his 'Pathologischen Untersuchungen,' showed clearly and distinctly that the contagia till then invisible must be regarded as living organisms, and gave his reasons for this view. … If we are forced to recognise the characteristic qualities of living beings in these contagia, there is no good reason why we should not regard them as real living beings, parasites. For the only general distinction between their mode of appearance and operation and that of parasites is, that the parasites with which we are acquainted have been seen and the contagia have not. That this may be due to imperfect observation is shown by the experiments on the itch in 1840, in which the contagium, the itch-mite, though almost visible without magnifying power, was long at least misunderstood. It was only a short time before that the microscopic Fungus, Achorion, which causes favus, was unexpectedly discovered, as well as the Fungus which gives rise to the infectious disease in the caterpillar of the silkworm known as muscardine. Other and similar cases occurred at a later time, and among them that of the discovery of the Trichinae between 1850 and 1860, a very remarkable instance of a contagious parasite long overlooked. Henle repeated his statements in 1853 in his 'Rationelle Pathologie,' but for reasons which it is not our business to examine, his views on animal pathology met with little attention or approval. It was in connection with plant-pathology that Henle's views were first destined to further development, and obtained a firmer footing. It is true that the botanists who occupied themselves with the diseases of plants knew nothing of Henle's pathological writings, but made independent efforts to carry on some first attempts which had been made with distinguished success in the beginning of the century. But they did in fact strike upon the path indicated by Henle, and the constant advance made after, about the year 1850, resulted not only in the tracing back of all infectious diseases in plants to parasites as their exciting cause, but in proving that most of the diseases of plants are due to parasitic infection. It may now certainly be admitted that the task was comparatively easy in the vegetable kingdom, partly because the structure of plants makes them more accessible to research, partly because most of the parasites which infect them are true Fungi, and considerably larger than most of the contagia of animal bodies. From this time observers in the domain of animal pathology, partly influenced, more or less, by these discoveries in botany, and partly in consequence of the revival of the vitalistic theory of fermentation by Pasteur about the year 1860, returned to Henle's vitalistic theory of contagion. Henle himself, in the exposition of his views, had already indicated the points of comparison between his own theory and the theory of fermentation founded at that time by Cagniard-Latour and Schwann. Under the influence, as he expressly says, of Pasteur's writings, Davaine recalled to mind the little rods first seen by his teacher, Rayer, in the blood of an animal suffering from anthrax, and actually discovered in them the exciting cause of the disease, which may be taken as a type of an infectious disease both contagious and miasmatic also, in so far as it originates, as has been said, in anthrax-districts. This was, in 1863, a very important confirmation of Henle's theory, inasmuch as a very small parasite, not very easy of observation at that time, was recognised as a contagium. It was some time before much further advance was made. … The latest advance to be recorded begins with the participation of Robert Koch in the work of research since 1876."

_A. De Bary, Lectures on Bacteria, pages 145-148._

"M. Pasteur is no ordinary man; he is one of the rare individuals who must be described by the term 'genius.' Having commenced his scientific career and attained great distinction as a chemist, M. Pasteur was led by his study of the chemical process of fermentations to give his attention to the phenomena of disease in living bodies resembling fermentations. Owing to a singular and fortunate mental characteristic, he has been able, not simply to pursue a rigid path of investigation dictated by the logical or natural connection of the phenomena investigated, but deliberately to select for inquiry matters of the most profound importance to the community, and to bring his inquiries to a successful practical issue in a large number of instances. {2147} Thus he has saved the silkworm industry of France and Italy from destruction, he has taught the French wine-makers to quickly mature their wine, he has effected an enormous improvement and economy in the manufacture of beer, he has rescued the sheep and cattle of Europe from the fatal disease 'anthrax,' and it is probable—he would not himself assert that it is at present more than probable—that he has rendered hydrophobia a thing of the past. The discoveries made by this remarkable man would have rendered him, had he patented their application and disposed of them according to commercial principles, the richest man in the world. They represent a gain of some millions sterling annually to the community. … M. Pasteur's first experiment in relation to hydrophobia was made in December 1880, when he inoculated two rabbits with the mucus from the mouth of a child which had died of that disease. As his inquiries extended he found that it was necessary to establish by means of experiment even the most elementary facts with regard to the disease, for the existing knowledge on the subject was extremely small, and much of what passed for knowledge was only ill-founded tradition."

_E. R. Lankester, The Advancement of Science, pages 121-123._

"The development of our knowledge relating to the bacteria, stimulated by the controversy relating to spontaneous generation and by the demonstration that various processes of fermentation and putrefaction are due to microörganisms of this class, has depended largely upon improvements in methods of research. Among the most important points in the development of bacteriological technique we may mention first, the use of a cotton air filter (Schröder and Von Dusch, 1854); second, the sterilization of culture fluids by heat (methods perfected by Pasteur, Koch, and others); third, the use of the aniline dyes as staining agents (first recommended by Weigert in 1877); fourth, the introduction of solid culture media and the 'plate method' for obtaining pure cultures, by Koch in 1881. The various improvements in methods of research, and especially the introduction of solid culture media and Koch's 'plate method' for isolating bacteria from mixed 'cultures, have placed bacteriology upon a scientific basis. … It was a distinguished French physician, Davaine, who first demonstrated the etiological relation of a microörganism of this class to a specific infectious disease. The anthrax bacillus had been seen in the blood of animals dying from this disease by Pollender in 1849, and by Davaine in 1850, but it was several years later (1863) before the last-named observer claimed to have demonstrated by inoculation experiments the causal relation of the bacillus to the disease in question. The experiments of Davaine were not generally accepted as conclusive, because in inoculating an animal with blood containing the bacillus, from an infected animal which had succumbed to the disease, the living microörganism was associated with material from the body of the diseased animal. This objection was subsequently removed by the experiments of Pasteur, Koch, and many others, with pure cultures of the bacillus, which were shown to have the same pathogenic effects as had been obtained in inoculation experiments with the blood of an infected animal."

_G. M. Sternberg, Manual of Bacteriology, page 6._

"In 1876 the eminent microscopist, Professor Cohn, of Breslau, was in London, and he then handed me a number of his 'Beiträge,' containing a memoir by Dr. Koch on Splenic Fever (Milzbrand, Charbon, Malignant Pustule), which seemed to me to mark an epoch in the history of this formidable disease. With admirable patience, skill, and penetration Koch followed up the life-history of bacillus anthracis, the contagium of this fever. At the time here referred to he was a young physician holding a small appointment in the neighbourhood of Breslau, and it was easy to predict, and indeed I predicted at the time, that he would soon find himself in a higher position. When I next heard of him he was head of the Imperial Sanitary Institute of Berlin. … Koch was not the discoverer of the parasite of splenic fever. Davaine and Rayer, in 1850, had observed the little microscopic rods in the blood of animals which had died of splenic fever. But they were quite unconscious of the significance of their observation, and for thirteen years, as M. Radot informs us, strangely let the matter drop. In 1863 Davaine's attention was again directed to the subject by the researches of Pasteur, and he then pronounced the parasite to be the cause of the fever. He was opposed by some of his fellow-countrymen; long discussions followed, and a second period of thirteen years, ending with the publication of Koch's paper, elapsed before M. Pasteur took up the question. I always, indeed, assumed that from the paper of the learned German came the impulse towards a line of inquiry in which M. Pasteur has achieved such splendid results."

_J. Tyndall, New Fragments, pages 190-191._

"On the 24th of March, 1882, an address of very serious public import was delivered by Dr. Koch before the Physiological Society of Berlin. … The address … is entitled 'The Etiology of Tubercular Disease.' Koch first made himself known, and famous, by the penetration, skill, and thoroughness of his researches on the contagium of anthrax, or splenic fever. … Koch's last inquiry deals with a disease which, in point of mortality, stands at the head of them all. 'If,' he says, 'the seriousness of a malady be measured by the number of its victims, then the most dreaded pests which have hitherto ravaged the world—plague and cholera included—must stand far behind the one now under consideration.' Then follows the startling statement that one-seventh of the deaths of the human race are due to tubercular disease. Prior to Koch it had been placed beyond doubt that the disease was communicable; and the aim of the Berlin physician has been to determine the precise character of the contagium which previous experiments on inoculation and inhalation had proved to be capable of indefinite transfer and reproduction. He subjected the diseased organs of a great number of men and animals to microscopic examination, and found, in all cases, the tubercles infested by a minute, rod-shaped parasite, which by means of a special dye, he differentiated from the surrounding tissue. 'It was,' he says, 'in the highest degree impressive to observe in the centre of the tubercle-cell the minute organism which had created it.' Transferring directly, by inoculation, the tuberculous matter from diseased animals to healthy ones, he in every instance reproduced the disease. To meet the objection that it was not the parasite itself, but some virus in which it was imbedded in the diseased organ, that was the real contagium, he cultivated his bacilli artificially for long periods of time and through many successive generations. {2148} With a speck of matter, for example, from a tuberculous human lung, he infected a substance prepared, after much trial, by himself, with the view of affording nutriment to the parasite. In this medium he permitted it to grow and multiply: From the new generation he took a minute sample, and infected therewith fresh nutritive matter, thus producing another brood. Generation after generation of bacilli were developed in this way, without the intervention of disease. At the end of the process, which sometimes embraced successive cultivations extending over half a year, the purified bacilli were introduced into the circulation of healthy animals of various kinds. In every case inoculation was followed by the reproduction and spread of the parasite, and the generation of the original disease. … The moral of these experiments is obvious. In no other conceivable way than that pursued by Koch could the true character of the most destructive malady by which humanity is now assailed be determined. And however noisy the fanaticism of the moment may be, the common-sense of Englishmen will not, in the long run, permit it to enact cruelty in the name of tenderness, or to debar us from the light and leading of such investigations as that which is here so imperfectly described."

_J. Tyndall, New Fragments, pages 423-428._

MEDICAL SCIENCE: 19th Century. The Theory of Germ Diseases.