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produce, or the extent of the misery caused. War is as nothing in destructiveness compared with pestilence. It therefore becomes the highest duty of the educated and humane physician to endeavour to prevent or counteract the influence of such a terrible enemy of his race. It is with the desire of fulfilling this duty that I have given my attention to the subject which I am about to bring under your notice.

I do not claim to be one of those laborious and noble band of investigators who have, by great industry and perseverance, cast a light, drawn from experiments, into the dark corners of the study of contagion, but I do claim to be one of those who, honestly taking advantage of those investigations, endeavour to apply them (as every practical physician of the present day should) to the prevention and cure of disease. In a recent lecture by Dr. Burdon Sanderson, he says:-"It may be said that it is no part of the business of the mere physiologist or pathologist to have any opinion on a practical question, but the present case (the consideration of the nature of infective processes) is entirely an exception." Dr. Sanderson then proceeds to express opinions favourable to the antiseptic treatment of wounds. Now, I do not agree with those who speak lightly of the "business of the mere physiologist or pathologist;" on the contrary, I think it is his duty to express his opinions upon practical questions; and it reflects discredit on many of the so-called practical physicians and surgeons that they do not attend more to his precepts, and that they neglect to apply them in practice. It may be true, as Dr. Sanderson says in the same lecture, that "in judging of the value of a therapeutical method, the one and only criterion is success;" but the ways to success are different, and while success has been obtained by blind empiricism, and more quickly by enlightened empiricism, yet the greatest and most rapid strides in practical medicine and surgery have been accomplished by the guidance of the "physiologist and pathologist," whom some affect to despise.

Our knowledge is small as compared with what it will ultimately become. It may be, indeed, that we have only got hold of a very few facts. Nevertheless, the facts that have been established are so valuable, and the hypotheses founded thereon so likely to be true, that the time has arrived when the title of these lectures is not inapplicable, and we are able to apply our knowledge of the intimate nature of contagion to practice; and where that knowledge is not British Medical Journal. February 9, 1878. Page 179.

yet sufficiently accurate to be of immediate practical application, yet it is sufficient to direct our efforts in the prevention or cure of disease, and enable us to avoid adopting and acting upon the false, though ingenious, theories of by-gone days.

I have thought this subject worthy of notice by such an audience as this, because I believe that many of the results of recent observations have been misinterpreted or misapplied, not only by the public, but by members of our own profession who have not, perhaps, had the time or the means of carefully weighing the difference of opinion, and estimating the value of the variety of facts which have, from time to time, been published within the past few years. It thus happens that four very different series of investigations have been more or less confounded by many inquirers, namely—

1st. Into the nature of fermentation.

2nd. Into the question of spontaneous generation.

3rd. Into the nature of septic infection.

4th. Into the nature of the contagium of specific diseases.

These four series of inquiries must be considered as consisting of two groups. The inquiries into the nature of fermentation and the probabilities of spontaneous generation constituting the first group are merely investigations concerning the beginnings of life and the nature of lower organisms, whether connected or not with the presence of disease. The other group of investigations is essentially of a pathological character; and the nature of septic infection, and the contagion of specific diseases, have direct bearings on scientific and practical medicine.

The main object of my lectures being to discuss the nature of infection and contagion, it would seem at first sight that my remarks should be confined to the third and fourth of the inquiries indicated above. If, however, I were to follow such a course, I would be promoting an error of the opposite character to that which I have condemned, and would be denying that there is any connexion between the four lines of investigation which I have enumerated. It must be admitted that all these lines of investigation do not run simply parallel to one another, but frequently interlace, and are closely related, though not necessarily connected with one another, and cannot be studied separately. The terms zymosis and zymotic have been used in medicine from the most ancient times down to the present day. It is scarcely necessary to mention that zymosis

means fermentation, and that it is derived from the Greek Çuμe, leaven-hence the term zymotic disease, which has been applied to certain diseases upon the supposition that the processes by which these diseases are developed bear close analogy to the process of fermentation, as observed in the fermentation of saccharine fluids or vinous fermentation. I wish to lay special stress upon the fact that it was the character of the vinous fermentation alone that suggested the application of the term zymotic to diseases, as, when it was first introduced into medicine, the vinous was the only fermentation studied, even if others were known; the term zymotic disease is now used as synonymous with infective disease. The use of the term zymotic is one which, I believe, has done more to retard the progress of the study of the diseases to which it is applied than most of the other numerous pathological misnomers with which we are troubled, and the use of the term has, I think, tended to impress upon the minds of even scientific observers the idea that observations upon fermentation of various kinds will determine the nature of the processes which take place in some of the infective diseases. I shall now discuss, as briefly as possible, the amount of light which the pathology of the infective diseases may derive from the study of fermentation. Probably the best definition of the term "fermentation" is that given by Professor Miller-namely, "Various transformations which organic compounds experience under the influence of a small quantity of organised matter, which is itself in a state of active alteration." "This active substance, which is termed a ferment, neither imparts anything to nor receives anything from the substance which is undergoing fermentation." In the vinous fermentation we find that the introduction of the yeast plant into a saccharine fluid determines the fermentation of such a fluid, and the conversion of the sugar contained therein into alcohol and carbonic acid. The yeast plant will not increase nor multiply in such a fluid, if it contain sugar only. The sugar will ferment but the plant will die. For the plant to continue its existence, a proper soil for it to grow upon must be provided, and this soil must contain nitrogenous elements to nourish the tissues of the yeast plant; but such growth and such pabulum is unnecessary for the production of fermentation alone. If the yeast plant be washed with distilled water, its power of fermentation is diminished-indeed, it may be temporarily suspended, although the life of the plant is not destroyed. It thus appears that the fermentation is caused by a Elements of Chemistry. Part III., 1857. P. 102.

a product of the growth of the plant-not by the plant itself. That an active principle, capable of itself producing powerful effects on other bodies, can be developed during the growth of such tiny organisms as the yeast plant, is just what might be expected when viewed by the light of the analogous results which take place during the growth of higher vegetable organisms. Thus the various poisons existing in vegetables are the products of the growth of the plants from which they are obtained. These agents, when separated from the plants, are not in any sense living, but are capable of producing as direful results upon human beings, the lower animals, or in some cases even upon plants, as any which have been attributed to disease germs. Some of these active principles may even be produced artificially.

I do not propose to discuss the various forms of fermentation, which seem now to be almost innumerable, but wish to call your attention to a process, strictly homologous to, if not identical with, fermentation, which has a most important bearing upon the question of the infective processes of disease.

There are certain little organisms whose name, "bacteria," is now in the mouth of everyone. They are as generally talked of as if those who discuss them were intimately acquainted with their appearance and nature. The name, in consequence of sensational lectures, has come to be commonly employed in the same sense as


disease germ; so bacteria and germs are now looked upon as almost equivalent to "plague and pestilence." Now bacteria in themselves appear for the most part to be harmless little creatures; they or their germs swarm in millions in the air we breathe, the fluids we drink, and the food we eat. They can be collected from our mouths at any time, and when washed clean by distilled water have been injected into the blood without producing any evil result. It is quite clear that if bacteria were possessed of the terrible powers attributed to them they would soon have the world to themselves, having eaten up or decomposed all other organised beings. In spite, however, of the apparent harmlessness of these bacteria, it seems now to be almost certain that their existence is necessary, though their presence not essential, to the production of some of the most terrible forms of zymotic or infective diseases with which we have to deal. One disease (anthrax) is said to depend upon them (Pasteur). It is at this point that the study of


• Proceedings of Academy of Medicine of Paris. July 3rd, 1877. Medical Record October, 1877. Pp. 428.

fermentation throws important light upon the nature of some forms of zymotic disease; it is because bacteria take part in a certain fermentation that they are important from one point of view. It is now agreed by all investigators that if septic material—that is, decomposing animal matters-be introduced into the blood of an animal, it produces poisonous effects. The result may be immediately fatal, or the effect may be slight and the animal recover, but of the effects of this poisoning I shall have more to say hereafter. A poisonous septic fluid may be prepared by infusing animal tissue (eg., muscle) in water, and when this becomes putrid, boiling it with alcohol, removing the alcohol by filtration and evaporation, and extracting it with water. This fluid contains septic poison, capable of destroying life, yet, whatever the poison be, it has not been destroyed by boiling alcohol. It has been proved by a welldevised and beautiful series of experiments that the poisonous fluid contains neither bacteria nor germs of any kind; the poisonous matter can, however, be filtered out by a porcelain filter. Now, having ascertained that the fluid containing the poison is free from germs, it is necessary to find out the source of the poisonous material. It arose from the putrid infusion of animal tissue, but how did it get there? It may be now considered as proved, by the observations of Dr. Burdon Sanderson and others, that this virulent poison is the product of a fermentation in the infusion of muscle, the fermentation being promoted by the presence of bacteria, just as the vinous fermentation is promoted by the yeast plant; the ultimate result in the former case being the septic poison in the latter, alcohol, or, as we may fairly call it, the alcoholic poison. I must here mention that the bacteria, which first appear in organic infusions or cultivating fluids, do not possess the power of producing a septic poison, but the succeeding generations produced by these bacteria do possess this power. The first generation of bodies do not present the same appearance as those which follow bacteria, having the appearance of little rods, produce as offspring, not rod-like bodies, but spheroidal bodies, called micrococci, which have a tendency to collect into masses (gloa) in which the bodies appear to cohere by means of a gelatinous substance. So much then for the relation of fermentative processes to the production of disease, and it amounts simply to this—that certain fermentations generate poisons, which in their turn may produce diseased conditions.

Reports of the Medical Officer of the Privy Council and Local Government Board. New Series, Nos. VI. and VIII.; and British Medical Journal, 1875, 1877, and 1878.

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