according to Hecker, and this writer estimates the mortality in Europe at 25,000,000. The accounts given by historians of the habits of living and surroundings of most of the populations thus scourged, are such as fully explain their exceptional liability, and find their counterpart in the condition of the Mohammedan pilgrims during the last epidemic of cholera you lately heard so graphically sketched by Dr. Little, as also in that of the Irish peasantry in the famine of 1847-1848. The other fact to which I have alluded is that each epidemic of contagious disease presents an uniform type, conformable to itself, not only in different places at the same time but also at different periods however remote, and that whenever exceptional forms and complications do occur these are due either to the co-existence of another epidemic or to special and exceptional forms of liability in the individual affected; the law being that with regard to the disease the poison has a special affinity or attraction for the organs or tissues according to its nature and the source from which it proceeded or was eliminated, as the skin and throat in scarlatina, the intestinal follicles and mucous membrane in cholera and enteric fever; and that with regard to the individual attacked those organs are found to become the seats of special complication which are specially predisposed in consequence of their undergoing increased disintegration or waste of tissue at the time of invasion of the disease. We thus explain the increased liability to suffer cerebral and nervous complications in fever of the hard worked and anxious student or professional man, as well as many other complications not belonging to the disease per se, but to be ascribed to some condition in the individual affected. Of the causes of liability or predisposition some are either inherent in our constitution, or in cosmical conditions not under our control, others being conditions in us or around us which are preventable and are therefore more peculiarly the subject of hygienic measures. We may glance for a moment at some of the former before entering on the consideration of the others. The first are those congenital or inherited constitutional peculiarities sometimes observed in an individual, sometimes in several members of a family, by virtue of which some persons appear to possess an absolute immunity from zymotic disease under any amount of exposure, while on the other hand, others succumb to its influence whenever exposed.
At a recent meeting of one of our Medical Societies, the case was mentioned of a lady whose liability to smallpox was such that she had suffered seven attacks of this disease. Nor is this a singular instance. Different members of a family not unfrequently share in this kind of susceptibility, and the records of medicine moreover contain numerous examples of a family predisposition to suffer some unusual or exceptional complication in the course of typhus or other zymotic disease. Of course these inherent and inherited forms of liability cannot be prevented, neither can the family tendency to certain complications be explained, farther than by supposing that there exists in such individuals not only conformity of type of structure, but also a conformity in those “affinities existing between definite tissues and definite substances, which must be referred to peculiarities of chemical constitution in virtue of which certain parts are enabled in a greater degree than others to attract certain substances from the neighbouring blood.”  Another non-preventable form of liability is that attendant upon the evolution of organs, and the rapid metamorphoses of tissue during the growth of the body. That the liability to certain diseases both diathetic and zymotic is most remarkable during the periods of childhood and adolescence is well known. We find the explanation of the fact, so far as it can be explained, in the greater activity of the formative process and consequently great necessity that the balance of forward and retrogressive change should be preserved, and moreover that the balance of evolution of the several organs should be so adjusted that none of the materials appropriate for the maintenance of any part may remain in the blood; “since each part, by taking from the blood the materials it requires for its nutrition, prevents the accumulation and excess of such matters in the blood as effectually as if they were separated from it and cast out by the excreting organs speciidly provided for that purpose.”t It follows of necessity that the period of growth and development is one of general liability, capable of being augmented by various agencies, extrinsic or intrinsic, till it amounts to predisposition or proclivity to disease. Another and remarkable example of liability, is that caused by the involution and disintegration of an organ which has fulfilled a temporary purpose in the economy, and the consequent presence of its effete materials in the blood. Such is
the case of the puerperal female whose liability to zymotic disease is well known. Dr. Moore has already illustrated the influence of season and of atmospheric changes as exciting causes of disease; they have also an influence on our organism, predisposing to diflerent types of disease as well as to different diseases at different periods. The researches of Dr. Edward Smith and other physiologists have shown that great variations in the vital processes occur at different periods of the year, and that an exaggeration of these constitutes a form of liability to disease, and impresses a type upon disease, varying according to the season, “the tendency generally being to sthenic and inflammatory forms of disease in spring when the amount of vital action is at a maximum, and to those of an asthenic type characterized by exhaustion in the latter end of summer and in early autumn.” “It appears, however, that the rule, though generally true, is not universally so, but that the effects of season are modified by the constitutional peculiarities of individuals, and that the selection of certain individuals as the earliest victims of an epidemic of influenza or cholera is due to the comparatively greater influence which certain external conditions exercise upon the vital powers of the system in these individuals.” There cannot be a doubt that the cycle of change of the seasons is adapted by the all-wise Creator to our bodily and mental constitution, and that any marked deviation from their order must be injurious, whether it be the unusual prolongation of a season, or its abbreviation, or the excess or defect of its characteristic phenomena. Thus, prolonged wet or drought, prolonged cold and frost, or prolonged summer heat, are each injurious. Warm and moist winters are proverbially unhealthy, as are cold, dark, and ungenial days, with deficiency of sunlight, in spring. The last especially predispose to typhus, while long, hot summers not only favour the generation of the malarial poisons, but moreover render the body predisposed to their reception and influence, more especially when passing suddenly into a cold and moist, because late, autumn. The last non-preventable predisponent I shall notice is that mysterious atmospheric agency which medical men recognise by the terms epidemic constitution, epidemic influnece, or, in the words of Inspector-General Lawson,
3. Health and disease as influenced by the cyclical changes in the human system chap. 6. t Army Medical Reports, 1861, page 405.
particles of our bodies; each organ or tissue attracting from the blood the materials adapted to its own growth or maintenance, while the products of retrograde metamorphosis— in other words the effete materials of the tissues—are resorbed into the blood, and by combination with its oxygen form new and devitalized compounds fit only to be eliminated or cast off by the various excreting organs; the carbonized^ products being chiefly eliminated by the lungs and liver, the azotized by the kidneys and other emunctories. It follows that this process of continual moleoular change necessarily involves the temporary presence in the blood of a variable amount of matters in a state of progress to decay, the elimination of which is essential to health. We know that this elimination and the preservation of health depends mainly on the healthy condition of the three factors of nutrition, the blood, the tissues, and the nervous system;  the first requiring healthy digestion, healthy respiration, and healthy secretion, for the preservation of that assimilating power it possesses, by which many noxious substances introduced into it from without are changed and made harmless, and ultimately eliminated; the second being equally necessary, inasmuch as the unhealthy tissue reacts upon the blood, furnishing oftentimes a permanent supply of noxious ingredients upon which a dyscrasia or blood disease depends. The necessity of a due supply of nervous influence for the nutrition of the body or of any portion is proved by numerous examples, as is also the important part in predisposition played by the exhaustion of this influence by excessive and long continued exercise, whether mental or bodily, anxiety, or other depressing emotion on the one hand, and the protecting power of the opposite condition of mental and physical energy and activity upon the other. In short, it will be found that so long as the functions of these several factors of nutrition are duly performed, and coadapted to each other, so long the equilibrium of health is preserved, and the reaction against morbific agencies is maintained; but if the health of the blood suffers by contamination from within the body or from without, to the loss of its assimilating power ; or the healthy metamorphosis of the tissues is interfered with; or an important excreting organ fails to exercise its depurative functions; or by some severe shock or prolonged strain the nervous influence is per-
5. Vide Sir James Paget’s Lectures on Surgical Pathology, lectures 1 and 2.
6. Vide Virchow’s Cellular Pathology, lecture 6.
7. Vide Paget, lecture 2.
verted or lost;” the continuous adjustment of internal relations to external relations ” in which healthy life consists* becomes imperfect, the reaction against external morbific agencies is no longer maintained; to the receptivity of these which exists in all constitutions is added the incapacity of assimilating and changing so as to eliminate them by excretion, in which proclivity or predisposition to disease essentially consists, and the zymotic poison being introduced from without —whether in the form of contagium particles detached from living diseased bodies, or of miasm emanating from other sources—its special dynamic effects are set up in the blood, and there follows disease conformable to its source or type, with local affections due either to the elective affinities of the poison for the organs or tissues in which the contagium is generated, or to pre-existing conditions of the organs thus affected; and, finally, the reproduction and diffusion of the contagium This view of the essential nature of predisposition corresponds with the explanation given by Dr. Carpenter of the mode of action of predisposing causes, viz.:— “That all the recognised predisposing causes of zymotic disease tend to produce in the blood an undue accumulation of azotized matter already in a state of retrograde metamorphosis, and therefore precisely in the condition in which it is most readily acted on by ferments, . . . and that the liability of each individual among a number who may be concurrently exposed to the same poison will mainly depend upon the degree in which his blood may be charged with the matters in question.” Dr. Carpenter’s theory not only explains the action of causes predisposing to disease generally, and to special complications in particular, but it also explains the injurious influence of the latter upon the disease, and the well known fact that the fatal termination of many cases of fever and scarlatina is due to continuous infection arising from the reception into the blood of the products of regressive change; constituting what are denominated by pathologists the secondary contaminations of febrile diseases. Under his first category of predisposing causes Dr. Carpenter classes putrescent food, water contaminated by decomposing matter, and contaminated respired air. Of the first no more striking example could be cited than that of the Faroe Islanders already referred to, whose extra-
8. H. Spencer’s Biology, vol. 2
ordinary liability to zymotic disease is to be accounted for by their diet, thus described by Dr. Parnum:— “During the many months that the fish, flesh, or fowl is neither fresh nor yet wind dried it is called ‘rast,’ a word which I can only translate by half-rotten. This appellation it fully deserves from the horrible smell that it sends forth, from its mouldy aspect, and the numerous maggots which swarm upon it. I have seen a boat’s crew of eight men eating with relish the raw flesh of the ca’ing whale, though it was so decomposed that the smell of it was disagreeable to me even in an open boat, and the bottom of the boat was almost white with the maggots that fell from the decaying mass.” We can scarcely wonder that on the introduction of the zymotic poison of measles nearly six-sevenths of the population were attacked, or that a most exhausting diarrhoea, often continuing for months, was a frequent sequel of the disease* Of the influence of contaminated water as a predisponent to cholera and enteric fever, and as powerfully augmenting the severity of these diseases, the proofs are so numerous and so well known that I need not dwell on them; besides you have already heard from Dr. Grimshaw abundant evidence of the intimate causal relation between this agent and zymotic diseases. The same remark applies to the respiration of the gases arising from decomposing human excreta or ” civic miasm,” but just as there are some individuals who, because contagion does not affect all who are exposed to its influence, do not be • It should be remarked that the evil effects of the excessive use of animal food are by no means exclusively confined to that in a state of putrescence. It is, however, not so much as a predisponent to zymotic disease as the cause of serious and often fatal complications that the influence of a too highly annualized diet is observed. The dangers of a state of rude health produced by full living have been thus graphically sketched by the late Mr. Travers:— “The state of rude health, as that phrase is commonly understood, I consider to be a forced state, that in which the nutrical powers are tasked to the uttermost and successfully struggle with a surplus of diet and stimulus, ridding the body of both by the action at its full stretch of every excreting organ. The subjects of this class are perpetually running upon the boundary between health and disease, a sudden shock deranging some important function destroys the equilibrium of the machine which its over pressed powers are the less capable of reinstating,” &c. Except in regard of nomenclature, there seems little difference between the teachings of a great surgeon of the last half century and those of the physiologists of the present day. I find predisposition to epidemic disease ascribed to the excessive use of animal food by Sims, in his description of a remarkable epidemic of typhus in 1771, and by Hecker in his account of the sweating sickness of 1517, which prevailed exclusively among men, “who,” says Hecker,” eat spiced meat to excess, but who were also addicted to nocturnal carousings, and drank strong wine on rising in the morning.”
lieve in its existence—at least as an essential element in the causation of disease—so there are others who, because individuals or families live for months and even years in the midst of filth, and habitually breathing air loaded with foecal miasma with apparent impunity, question the influence of such miasm as a source of the poison of fever, or exciting cause of the disease. The answer to this objection is, that immunity under such circumstances is owing to the power which the blood possesses of assimilating and rendering innocuous noxious matters received into it from without. It is this power of adaptation or acclimatization which enables the inhabitant of the Faroe Islands to live upon putrefying flesh without suffering anything more than ordinary diarrhoea unless during epidemic visitations; which accounts for the fact that the native of tropical malarious districts can reside in the vicinity of the swamp which is fatal to the European stranger; which long made French physicians regard the enteric fever of Paris as a disease peculiar to the strangers visiting that city; and which enables many medical men, nurses, and hospital servants to pass years in the midst of infection with impunity. But whatever opinion may be entertained with regard to civic miasm as an exciting cause, its influence as a predisponent cannot be questioned, both as rendering the constitution more liable to zymotic diseases in general, and as determining their special complications. The histories of the epidemics of zymotic diseases of the present day abundantly prove this, as do the descriptions given by Hecker and others of the abounding filth of the persons and dwellings of the English during the epidemic periods of the middle ages, and the evident causal relation between the diseases and these conditions. In such cases we frequently find that a period of deranged health precedes the outbreak of fever, characterized by gastric derangement, headache, languor, and unhealthy secretions; and observations made by medical men at different times and in different places have shown that in this premonitory stage the blood undergoes a change recognisable by the microscope, the red corpuscles being broken up and the serum tinged by their contents* Dr. Grimshaw has adduced abundant proof of the power. This fact, first observed by Dr. Potter of Baltimore, and again by Dr. Cormack, in the Edinburgh relapsing fever of 1843, has been more recently recognised and described by 1 Dr. Hand of Philadelphia. Dr. Hand relates a case in which the blood was examined within three or four hours of the first seizure and found to be in an average state of degeneration. The case proved a typical one of relapsing fever. Dr. Hand believes that by living in a contaminated atmosphere the blood
pens that pestilential diseases most certainly follow in the wake of a famine, and carry off a far greater number than perish from actual starvation.” Such was the case in the Irish famine of 1846-7 the effects of which are thus graphically described by an eyewitness—Dr. Donovan of Skibbereen. ‘”In a short time the face and limbs became frightfully emaciated; the eyes acquired a most peculiar stare; the skin exhaled a peculiar and offensive fsetor, and was covered with a brownish filthy coating, almost as indelible as varnish. This I was at first inclined to regard as incrusted filth, but further experience has convinced me that it is a secretion poured out from the exhalents on the surface of the body. The sufferer tottered in walking like a drunken man; his voice became weak like that of a person in cholera; he whined like a child, and burst into tears on the slightest occasion. As regards the mental faculties their prostration kept pace with the general wreck; in many a state of imbecility, in some almost complete idiotism,’ ” &c.  The highest degree of predisposition of which the living body is susceptible is generated by the crowding together in gaols, workhouses, or hospitals of human beings in the condition above described, as is proved by the annals of’the epidemic of 1847-8 already referred to. Fatigue and exhaustion caused by prolonged or excessive bodily and mental exercise is one of the most powerful predisponents to zymotic disease. We see its influence in the persons of anxious relatives who succumb to infection when exhausted by long watching; and it is witnessed in the case of cholera in soldiers exhausted by long marches in a hot climate, more especially if conjoined with intemperance in the use of spirits. Under such combined conditions we have increased disintegration of muscular tissue, involving an increased accumulation in the blood of carbonized and nitrogenous products in a state of progress to decomposition, and diminished oxidation of effete tissue due to imperfect respiration, and to the superior attraction of the alcohol for oxygen—heat and alcohol here acting under Dr. Carpenter’s third catagory, namely, by obstructing the elimination of the products of disintegration of muscular tissue already augmented by excessive exertion. We are indebted to the Rev. Professor Haughton for the remarkable observation that the amount of nitrogenous products of metamorphosis of tissue from mental work exceeds that accruing from bodily labour in the proportion of 533 grains to 400 grains of urea excreted daily.
9. ” Principles of Physiology,” sixth edition, t Dublin Medical Frets, vol. xix, page 67.
He also states that “whenever an abnormal amount of these products is excreted the cause must be ill health, and most generally that most fatal of all diseases to which man •is liable, anxiety of mind, a vague and unscientific expression,” says Dr. Haughton, “which, however, denotes a real disease.”* There may be said to be two distinct modes of action of mental, or more properly speaking emotional, predisposing causes, viz., by long continued strain and by sudden shock. Carking care, anxiety, and despondency act in the former manner as true predisponents; sudden and violent emotions of grief, shame, and terror act in the latter, and may be more properly termed determining causes. Both exercise a powerful influence on the molecular nutrition as we have already seen in the case of the first; a striking example of the influence of terror on this function is thus narrated by Mr. Carter:—” A lady who was watching her little child at play saw a heavy sash fall upon its hand cutting off* three of the fingers, and she was so much overcome by fright and distress as to be unable to render it any assistance. A surgeon was speedily obtained, who having dressed the wounds turned himself to the mother, whom he found seated moaning and complaining of pain in her hand. On examination, three fingers corresponding to those injured in the child were found to be swollen and inflamed, though they had ailed nothing prior to the accident. In four-andtwenty hours incisions were made into them, and pus was evacuated, sloughs were afterwards discharged and the wounds subsequently healed.”  It is well known that under the influence of strong emotion the blood and secretions will undergo important changes, the surface will become pallid, or it may be suffused with bile, the mother’s milk will become a deadly poison to the infant at the breast, and in many cases of fever recorded by Sir H. Marsh, Dr. Law, and others, in which such emotion has been the determining cause the entire course of the disease has been characterized not only by severe nervous symptoms but also by marked changes in the blood, and lesions of the function of nutrition. The conclusions which I think we may draw from the facts which I have adduced, are the following: —
I. That liability to zymotic disease is inherent in our constitution, involved so to speak in the function of nutrition.
10. Dublin Quarterly Journal of Medical Science, voL 30. t On Hysteria, quoted by Dr. Carpenter.
II. That it varies in degree in different individuals, and in the same individual at different times and under different conditions, partly external or extrinsic, partly internal or intrinsic, some of which are preventable and others nonpreventable in their nature.
III. That, ceteris paribus, this liability is least in those persons in whom healthy blood, healthy tissues, and healthy excretions, and a healthy state of the nervous system constitute a healthy nutrition.
IV. That is greatest in those whose blood contains the largest amount of the products of waste of the tissues, or of matters in a state of decomposition introduced into the circulation from without.
V. That all scientific hygienic measures are based upon their power of preserving or restoring the healthy condition of the factors of nutrition and neutralizing the conditions, whether extrinsic or intrinsic, by which this function is impaired or deranged.
VII.—On Antiseptics and Disinfection. A Lecture delivered by Robert Macdonnell, Esq., M.D., F.R.S., Surgeon to Dr. Steevens’ Hospital.
The impurities existing in the atmosphere which surrounds us are partly gaseous, and in part minute but solid particles of matter. The gaseous impurities which render air more or less deleterious, such as the carbonic acid gas which accumulates in a crowded room, or the sulphuretted hydrogen which emanates from the sewer are detected by chemical agents. Chemistry has taught us how to recognise these impurities and how to remove them. Many gaseous impurities in the air we detect by the sense of smell, but some being inodorous can only be proved to exist in it by chemical re-agents. When, therefore, we remove disagreeable smells, and so far purify air as to cause it no longer to be offensive to our nostrils, it by no means follows that it is thereby rendered healthful and pure. It is a dangerous delusion to repose trust in that class of agents called “deodorants”; they are very useful in their way when their true use is comprehended; in so far as they render air less disagreeable to our noses they are good; if thereby we are induced to suppose that the air is purified and rendered wholesome we are led into error. It must ever be borne in mind that no chemical disinfectants can supply the place of cleanliness, ventilation, and drainage. But it is not to the gaseous impurities of the air we breathe that I desire at present to direct attention. It is to the other class of impurities of which I have spoken: the exquisitely minute but solid matter in suspension in the air; the almost inconceivably fine dust which dances in the sunbeam, and is borne across the ocean by the storm. The offensive gases given oft” from decomposing organic matter are usually either ammonia or compounds of hydrogen with carbon, sulphur, or phosphorus. Such impurities as these are absolutely invisible. Thanks to the marvellous delicacy of the means of investigation introduced through the influence of light, we are now enabled to render visible the dust, minute though it be, which floats in our atmosphere.
Having exhibited a variety of experiments, as set forth by Professor Tyndall, to illustrate this subject, the lecturer proceeded to say:—After such evidence as is now before us no one can doubt the large quantity of organic filth which, in the shape of dust, loads the atmosphere of cities, nor is the country free from its pollution. Even far out at sea, and on the summits of mountains, these light bodies may be met with. A phial of perfectly pure, newly-fallen snow, was taken from the summit of Mont Blanc, by Dr. Kolbe, and brought to M. Pouchet. On melting it it yielded about one cubic inch of water, which was to all appearance pure and clear. But a slight deposit was observed in it on standing, and this deposit contained the following substances:—A few minute bodies of a mineral nature, two woollen filaments, one white and one blue, a fragment of a confervoid plant, a minute tuft of vegetable air tubes, and a dozen young cells of Protococcus Nivalis. Thus we find that the force of the wind may bear, even to the Alpine summits, dust containing mineral matter, organic matter, and spores. As regards the ” germ theory ” of disease, and as it may be called the “germ or putrefaction theory” of suppuration, science owes much to discussion arising upon a very different topic—viz., that of “spontaneous generation.” Two able disputants arose in M. Pasteur and M. Pouchet, whose investigations, although undertaken with quite another object, have yielded a rich harvest in this field. M. Pouchet declared that all his examinations showed the atmosphere to be everywhere poor in organic germs, and often entirely destitute of them; and that its capacity for generating animal life resided not in these germs, but in the general vivifying power of the air. M. Pasteur, on the other hand, insisted that the chemical constitution of the air remaining the same, its power of producing organic life varied with the locality from which it was taken; and this because the number of germs contained in it varied in different places. Both the disputants stated their positions in definite terms. M. Pouchet said, “I assert that from whatever region of the globe I take a quantity of atmospheric air, if this air be placed in contact with a putrescible liquid in hermetically-sealed vessels, the liquid will invariably become filled with living organisms.”
M. Pasteur said, ” It is always possible to obtain in a particular locality a notable volume of atmospheric air which, without having been subject to any physical or chemical modification, is nevertheless incapable of exciting any change whatever in a putrescible liquid.” These assertions, emanating from two eminent observers, both members of the Academy, were so diametrically opposed to each other, that it was agreed to refer them to a Committee, in whose presence the requisite experiments should be performed, and who should report to the Academy on the result. Such a Committee, composed of five members, was accordingly formed, and entered upon its labours in June, 1864, in the Chemical Laboratory of the Museum of Natural History, at the Garden of Plants. M. Pasteur first presented three of his flasks which had been filled with air four years previously on the Montanvert, and had remained ever since perfectly unchanged. One of them was opened under mercury, and the air which it contained, on being analyzed, was found to have the natural constitution of the atmosphere (twenty-one parts of oxygen to seventy-nine parts of nitrogen). Another flask was opened by a minute orifice at the neck, and after being left for three days exposed to the atmosphere, it contained flakes of a cryptogamic vegetable growth, which subsequently became largely developed. M. Pasteur then prepared and sealed, before the Committee, sixty flasks, similar to those previously used. Nineteen of them, after cooling, were opened and immediately resealed in the amphitheatre of the Museum; nineteen on the top of the dome of the same building, and eighteen others at a countryhouse a few miles from Paris, under a thick growth of poplars. Afterwards microscopic vegetations were developed in five flasks of the first set, six of the second, and sixteen of the third. All the remainder were unchanged at the end of over four months. The Committee subsequently reported the result of their experiments, and gave as a conclusion that the facts observed by M. Pasteur, and contested by M. Pouchet, were of the most absolute exactitude. It thus seems to have been placed beyond a doubt that the atmosphere is incapable, from its chemical constitution alone, of exciting organic growth in a boiled infusion; but that it often introduces with it into the solution invisible germs which have this effect, the proportion in which these germs are present varying with the locality from which the air is derived. But up to this time the dispersion of organic germs in the atmosphere was not an actually observed fact, but only a probable inference from the results of experiments like the above. This is what gave a certain weight to the objection of M. Pouchet when he said in one of his communications, “It seems to me that when an experimenter declares that he can collect from the atmosphere either the eggs or spores of microscopic organisms, we have a right to demand that he should show them to us.”
No one, in fact, had succeeded in collecting these germs from the air in any abundance, in such a form as to be visible and recognised. This, however, was accomplished by Dr. Lemaire in 1864. He adopted the plan of condensing the vapours of the atmosphere in glass tubes by means of artificial cold. The moisture thus obtained was then kept in the tubes, well stoppered, together with an equal or double volume of air, at a temperature of from 73° to 86° Fahr. The collections were made in the month of July, from a marshy neighbourhood in the country, from the Garden of Plants in Paris, and from a village near the city, situated at two or three hundred feet higher elevation. The liquid, when first condensed, was colorless and limpid. It contained microscopic vegetable germs or spores; a great number of pale cells, of different dimensions; a considerable abundance of very small semi-transparent bodies (thought to be the germs of future infusoria) of a spherical, ovoid, or cylindrical shape, sometimes regular and sometimes irregular; certain brownish corpuscles, apparently of vegetable origin; starch-grains, dust-particles, and cubical crystals. Within twenty-four hours afterwards there were developed an abundance of living infusoria, bacteria, vibrios, spirilla, and monads, together with ramified cryptogamic vegetations. Exactly in proportion as the cryptogamic vegetations and the infusoria were developed, the spores and the small semitransparent corpuscles were found to disappear. Thus the actual existence of organic germs in the atmosphere was demonstrated; and there could no longer be any doubt that these germs, when introduced into an organic infusion, are abundantly sufficient to account for the production of infusorial and vegetative life. The Lecturer, in order to enable his .audience more accurately to comprehend the exact form of M. Pasteur’s experiment, exhibited the mode of hermetically sealing up flasks containing fermentable liquid. M. Pasteur took glass flasks filled partially with a clear infusion of brewer’s yeast. He then boiled the fluid, and while ebullition was going on actively drew out the necks of the flasks to a narrow point and sealed them over the flame of a blow-pipe. The fermentable liquid was thus enclosed in an air-tight vessel containing nothing save its own rarified vapour. Upon cutting off the neck of the flask in any particular place, the air of” that place rushed in to fill the vacant space. The flask being then resealed the effect of this air and (of such germs as it might happen to carry in along with it) upon the liquid could be observed.
He prepared sixty of these flasks. Twenty of them wore afterwards opened and resealed in the country at the foot of the first plateau of the Jura range. Twenty others wero opened and resealed on one of the Jura mountains, two thousand five hundred feet above the level of the sea, and the remaining twenty near the “Mer de Glace” Glacier, at an altitude of six thousand feet. The result was that of the first twenty flasks, eight were found afterwards to have produced living organisms; of those filled with air from a point two thousand five hundred feet above the sea level, five showed similar productions; while of those filled at the “Ifer de Glace ” one only became the seat of organic life. We see then that the air of our large cities is loaded with dust in part either mineral or lifeless organic debris, but partly composed of matter in the shape of germs or spores capable under certain circumstances of starting into organic life and growth. Nor is the air of the country or the mountain top quite free. Although ordinary light permits this dust to escape our observation, a strong beam causes it to become a real visible existence; painfully real when we come to contemplate with the aid of the electric beam the fine filth which we every moment draw into our lungs. It is, however, quite certain that air so laden with dust of one kind or another as to be positively irritating to the air passages, and even capable of gradually developing diseases peculiar to certain trades is not necessarily charged with that kind of matter ” living dust,” as Professor Lister aptly calls it, which is so very deadly to man; which in fact is conceived in the present day to be the means of propagating epidemic disease. The question is what is this portion so virulent in its nature, so mysterious in its development, so terrible in its attacks upon mankind? The current theory some time ago concerning epidemic diseases was that they were propagated by a kind of malaria consisting of organic matter in a state of motor-decay, and that such matter entering the body spread there the destroying process which had attacked itself. This theory was exactly analogous to that held with regard to the supposed action
VOL. VII.—NO, L K
of yeast. A little leaven leavened the whole lump. The discovery made hy Cagniard de la Tour in 1836, and independently by Schwann of Berlin in 1837, altered the views of chemists with regard to the theory of fermentation, and gradually altered the view hitherto taken as to the causation of epidemic diseases. By the discovery of the “Yeast plant,” a living organism capable of feeding, growing, reproducing itself, fermentation was proved to be a product of life, not a process of decay; a decomposition if you will, but a decomposition caused by the energy of growth and life. As regards fermentation the minds of chemists, influenced by the authority of Gay-Lussac for a time ascribed putrefaction to the action of oxygen, and retained the idea of matter in a state of decay. Pasteur however finally exploded this notion. He proved that the so-called ferments are not such; but that the true ferments are organized beings which find in the reputed ferments their food. Side by side with these researches and discoveries concerning ferments and fermentation has run the “germ theory” of disease. It is true that it is in a great degree an hypothesis based upon analogy, and every philosopher will admit that in such matters analogy may be but a deceitful guide. It has however received much strengtheningand support from various scientific observations. Unconsciously perhaps the mind is prepared to accept such a theory by learning the strange history of the invasion of the minute entozoon known as the “Trichina spiralis.” Dr. J. Burdon Saunderson’s experimental inquiries relating to the nature of infective agents has done much in the same direction. The researches of this able observer go to show that in all infective inflammations in the lower animals microzymes (microscopic organisms) abound in the exudation liquids; and that the same forms are to be found in the blood of animals when in the state of acute infective fever. To turn, however, from these refined scientific observations and ingenious theories to their practical application, the question is, how can we best escape the dangers which beset us on every side from the living organic impurities of the atmosphere 1 Obviously by seeking to free the air from these impurities. As to “deodorants” the risk of trusting to them simply has been already spoken of, they have, however, a recognised value. Various kinds of charcoal (peat charcoal, boghead coke, &c), quicklime, chloride of lime, a variety of metallic salts, dry earth, &c, have the power of either removing by their absorbing power offensive gases or of breaking them up by their chemical action. Ammonia, and several of the compounds of hydrogen, with carbon, sulphur, or phosphorus, not unfrequently given off by decomposing animal matter, may thus be got rid of.
True disinfectants or oxydizers of organic matter are more valuable as well as safer. The fumes of nitric and nitrous acids, the manganates and permangates of soda and potash, chlorine gas, &c, are powerful oxydizers, and quick lime, and chloride of lime owe in fact their deodorizing qualities to the same cause. Antiseptics, or those bodies which restrain or absolutely prevent decomposition, are in many respects the most important. Disinfectants oxydize the products of decomposition; antiseptics prevent the formation of any such products. The ordinary processes of cooking, pickling, tanning, &c, are to some extent antiseptic processes. Various metallic salts, sulphurous acid, creasote, and carbolic acid have remarkable antiseptic powers. Small quantities of the last named acid added to an organic solution completely prevent the growth of those organisms which cause, or at least accompany, decomposition. The careful use of it has been found to produce the best results in the treatment of open wounds. It seems to kill the “living dust,” which, penetrating along with the air into open wounds, causes the blood to rot and the system to be infected by a poison thus generated within itself. The whole range of modern scientific research does not possibly offer a more charming illustration than this topic of the antiseptic treatment of wounds of how science and practice work hand in hand for the benefit of mankind. When the philosophers of Bologna discovered and investigated the elementary phenomena of galvanism they little thought that in the starting muscles of a dead frog’s limb lay the germ of that which would one day bind the remotest corners of the earth together with telegraph wires. The discoverer of formic acid little dreamed at the moment that chloroform and its accompanying blessings lay hid in his discovery. Pasteur, Pouchet, Tyndall, and many others now see in the practical application of Professor Lister the benefits arising to mankind from purely scientific investigation, undertaken in fact with a view to elucidate questions of a very different nature. Professor Lister, of Edinburgh, combining in himself the rare qualification of the acuteness of the man of science, the skill of the experimenter, and the dexterity of the surgeon, has based on a scientific foundation a mode of practice which disarms of their dangers many of the worst injuries and the gravest operations.
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