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CHAPTER XIX.

DISINFECTION AND DEODORIZATION.

THE term disinfectant, which has now come into popular use, has unfortunately been employed in several senses. By some it is applied to every agent which can remove impurity from the air;' by others, to any substance which, besides acting as an air purifier, can also modify chemical action, or restrain putrefaction in any substance, the effluvia from which may contaminate the air; while, by a third party, it is used only to designate the substances which can prevent infectious diseases from spreading, by destroying their specific poisons. This last sense is the most correct, and it is that which is solely used here. The term disinfectant might also be applied to substances destroying entozoa or ectozoa, or epiphytes or entophytes, but there is a disadvantage in giving it so extended a meaning. The mode in which the poisons are destroyed, whether it be by oxidation, deoxidation, or arrest of growth, is a matter of indifference, provided the destruction of the poison is accomplished. The general term air purifier is given in this work to those agents which in any way cleanse the air, and which therefore include disinfectants; and the term sewage deodorants, to those substances which are used to prevent putrefaction in excreta, or in waste animal or vegetable matters, or to remove the products of putrefaction. In a great many instances the substances which are recommended as disinfectants are little more than deodorants, and ought properly to be spoken of as such.

The chief human diseases which are supposed to spread by means of special agencies (conveniently designated under the name of "contagia")," are, the exanthemata; typhus exanthematicus; enteric (typhoid) fever; relapsing fever; yellow fever; paroxysmal and the allied remittent fevers; dengue; cholera; bubo-plague; influenza; whooping-cough; diphtheria; erysipelas; dysentery (in some cases); puerperal fever; syphilis; gonorrhoea; glanders; farcy; malignant pustule; and, perhaps, phthisis. There

are some few others more uncommon than the above.

It has long been a belief that the spread of the infectious diseases might be prevented by destroying the agencies in some way, and various fumigations, fires, and similar plans have been employed for centuries during great epidemics.

In order to apply disinfection in the modern sense of the term, we ought to know-1st, the nature of these contagious agencies; 2d, the media

1 Tardieu, for example, Dict. d'Hyg., art. “Désinfection," and many other authors. It will be seen that the old distinctions between infectious and contagious diseases, and between miasmata and contagia, are not adhered to. They were at no time thoroughly definite, and are now better abandoned.

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through which they spread; and 3d, the effect produced upon them by the chemical methods which are supposed to destroy' or modify them.

1. THE NATURE OF THE CONTAGIA.'

This point is at present the object of eager inquiry. In the case of one or two of the above diseases, the question has been narrowed to a small compass. In variolous and vaccine discharge, and in glanders, the poison certainly exists in the form of solid particles, which can be seen by high powers as glistening points of extreme minuteness. In cattle plague blood-serum there are also excessively small particles discovered by Beale, which are probably the poison. The size of the particles supposed to be contagia is minute; some of them are not more thanth of an inch, and Beale believes that there may be smaller still to be discovered with higher powers. Chauveau has washed the vaccine solid particles in water; the water did not become capable of giving the disease; the washed particles retained their power. The epidermic scales of scarlet fever and the pellicle of the diphtheric membrane certainly contain the respective poisons, and after exposure to the air for weeks, and consequent drying, still retain their potency. It is more likely that solid matters should thus remain unchanged than liquids, but it has not yet been proved that this is so, and at present the exact physical condition of the contagia of the other infectious diseases remains doubtful.

The extraordinary power of increase, and capability of producing their like, possessed by some of the contagia when placed under special fostering circumstances, as in the bodies of susceptible animals, lead to the belief that they are endowed with an independent life. The old doctrines that they are simply either poisonous gases or animal substances in a state of chemical change, and capable of communicating this change, or that, like the so-called ferments (ptyalin, pancreatin, diastase, emulsin), they split up certain bodies they meet, are not now in favor.

The retention of the power of contagion for some time, and its final loss, the destruction of the power by antiseptics which do not affect the action of such bodies as ptyalin or diastase, and the peculiar incubative period which is most easily explained by supposing a gradual development of the active agent in the body, are more in accordance with the hypothesis of independent life and power of growth.

The independent living nature of the contagia is a belief which has long been held in various forms. At the present time there are three views, each of which has some arguments in its favor.

(1) The particles are supposed to be of animal origin, born in, and only growing in the body; they are, in fact, minute portions of bioplasm (to use Dr. Beale's phrase), or protoplasm."

This is the old doctrine of "fomites" expressed in a scientific form, and supported by a fact which was not known until recently. This is that the independent life ascribed to these particles of bioplasm is no assump

See Report on Hygiene for 1872 (Army Medical Department Report, vol. xiii.).

2 The observations of Chauveau, Beale, and Burdon-Sanderson, and still more recently, of Braidwood and Vacher, prove this very important point by what seems indisputable evidence. It does not follow that all small bodies are in such fluids the contagia, but the experiments prove that some of them must be. In many kinds of blood there are numerous small particles, derived, according to Riess, from retrograde metamorphosis of white blood-cells and which have no contagious property.

3 This view has been advocated with great force by Beale (Disease Germs, 2d edition); and Morris (The Germ Theory of Disease, 2d edition).

tion, since we are now aware that many of the small animal-cells or bioplastic molecules are virtually independent organisms, having movements, and apparently searching for food, growing, and dying.

This view explains singularly well the fact of the frequent want of power of the contagia of one animal to affect another family; as, for example, the non-transference of many human diseases to brutes, and the reverse. It also partly explains the non-recurrence of the disease in the same animal by supposing an exhaustion of a special limited supply of food, which cannot be restored, since it may be supposed that some particular bodily structure is altogether destroyed, as, for example, Peyer's patches may be in enteric fever. One objection to this view is, on the other hand, that living animal particles die with great rapidity after exit from the body, while the contagia do certainly last for some considerable time.'

(2) The particles have been conjectured to be of fungoid nature, and to simply grow in the body after being introduced ab externo. This view is supported by the peculiarities of the rapid and enormous growth of fungi, by their penetrative powers and splitting-up action on both starchy, fatty, and albuminoid substances, and by the way in which certain diseases of men and animals' are undoubtedly caused by them. It is clearly a view which would explain many phenomena of the contagious diseases, and has been supported by the experimental evidence of Hallier and many others, who have believed either that they have invariably identified special fungi in some of these diseases, or that they have succeeded in cultivating fungi from particles of contagia. At the present time, however, the evidence of true, recognizable and special fungi being thus discovered and grown, and forming the efficient causes, is very much doubted by the best observers. The micrococci of Hallier, supposed to be formed by the disintegration of the protoplasm of fungi, which Hallier considers can again develop to fungi, are looked upon by many as mere detritus."

(3) The particles of contagia are thought to be of the nature of the Schizomycetes, i.e., of that class of organisms which Nägeli has separated from the fungi, and which form the lowest stratum at present known to us of the animate world. They are termed Bacteria, Bacilli, Microzymes, Vibrios, Spirilla, Monads, etc. Their relation to the fungi, or to the Oscillarineæ, to which they are perhaps closer, is yet a matter of warm debate. That these creatures are concerned in many diseases is clear. Lister's genius first brought their practical importance forward, and the late re

1 A modification of this view, under the name of the Glandular Origin of Disease, is advocated by Dr. B. W. Richardson, F. R.S. (Address to the Sanitary Institute of Great Britain, Leamington, 1877; Nature, No. 414, October 4, 1877, p. 480). Admitting that the disease poison generally comes from without, he looks upon its action as catalytic, causing an altered glandular secretion or a change in the blood, the changed secretion reacting on the nervous centre supplying the gland or glands. He also conceives that during epidemic periods a strong nervous impression may have the same effect as the direct introduction of poison from without, so that the disease may occasionally arise spontaneously. He looks upon many diseases as hereditary, in the sense that the condition of the child resembles that of the parent, and will therefore be open to similar influences.

*Not only some skin and hair diseases of men and animals, and diseases of insects and fishes, are caused by the growth of fungi which fall on the surface of the body, or are drawn into the mouth, but internal diseases are caused by the growth of undoubted fungi, such as Aspergillus.

The supposed fungus, which Klein (Reports of the Medical Officer of the Privy Council, new series, No. vi., 1875) thought he had discovered in the patches of typhoid ulceration, was shown by Creighton to be merely an altered condition of fibrine simulating an independent organism (see Proceedings of the Royal Society, June 15, 1876).

searches of Klebs, Recklinghausen, and others, have shown how great a part they play in the production of Septicemia. The carbuncular disease of cattle and sheep (splenic apoplexy) is also intimately connected with Bacilli; and if the observations of Coze, Feltz, and others are correct, the same is true of typhoid fever. Ferdinand Cohn has asserted,' that even the glistening particles of vaccine lymph are Bacteria. Bacteria have been proved to cause disease of the intestinal mucous membrane, the uterus, the kidneys, and the heart, and they play some part in hemorrhagic smallpox. Bacilli were found to be the active agents in the poisoning by ham at Welbeck. Klebs and Tommasi-Crudeli have shown the probability of malarial poisoning being due to a Bacillus. Still more recently, Koch has essayed to connect phthisis with a similar organism. The peculiar form of febrile disease observed at Aberdeen by Dr. Beveridge was distinctly connected with the existence of minute organisms in milk. The researches of Pasteur on fowl cholera and charbon have shown not only that those diseases are due to Bacteria, but that they can probably be prevented or modified by inoculation with cultivated virus.

2

Yet in some of the epidemic diseases no Bacteria have been as yet demonstrated. In cholera, Lewis and Cunningham have failed, in spite of the most persevering search, to find Bacteria (or fungi) in the discharges or blood of cholera.

The reasons for attributing in many cases great influence to Bacteria, which are undoubtedly present, are obvious enough.

They are so widely spread in nature (in both air and water); their powers of growth, by division, are so wonderful; their food (ammonia, phosphates, and perhaps starches or sugars) is so plentiful, and their tenacity of life so great, that it is no wonder great consequence is now attached to them. Yet it is their very universality which is the strongest argument against the view that they constitute the contagia of any of the specific diseases, and any one who considers the peculiar spread of the contagious diseases will admit the force of this objection. To meet this objection it has been surmised that they are not the contagia, but merely their carriers. This view has not been defined; but as the plasma of Bacteria is albuminoid, it may perhaps be taken to mean that while the Bacteria are usually harmless, their plasma may become, in certain cases, altered in composition, and then becomes poisonous in different specific ways. Bacteria feeding in the blood of a typhus patient will become nourished with morbid plasma, and thus, so to speak, it is diseased Bacteria which become dangerous. We get here beyond the range of present observation, and are conscious how impossible it is with our present instruments to investigate such an hypothesis."

The belief which some entertain that Schizomycetes are the efficient agents of the contagious diseases has led to a number of experiments on the destruction of Bacteria by heat and by chemical agents, in the belief that the doctrine of disinfection was thereby elucidated. This could hardly be

1 Virchow's Archiv, Band iv., p. 229 (1872).

2 See note by Professor Ewart, Proceedings of the Royal Society, 1881, vol. xxxii., p. 492.

'For further information, see the "Address in Medicine," by W. Roberts, M.D., F.R.S., delivered at the Manchester Meeting of the British Medical Association, 1877 (Brit. Med. Journal, No. 867, August 11, 1877, p. 168). Also Professor Tyndall's papers in the Royal Society's Proceedings and Transactions (see Transactions of the Royal Society, 1876, part i., p. 27); Floating Matter in the Air, by the same author; Nägeli's Niedere Pilze; Fodor's Untersuchungen, op. cit.

the case, unless we are certain that the Bacteridia are the contagia, which is not yet proved to be the case. Disinfection must rest at present on its own experimental evidence.

The belief in the part played by Bacteridia has led also to much interest being taken in the discussion on ferments, and in the question of spontaneous generation, as it is imagined that a clew might thus be found to the origin, de novo, of the contagia. Mr. Darwin's doctrine of Pangenesis has even been pressed into the discussion, though it rather makes the darkness greater than before. It is curious to find so practical a matter as that of disinfection brought into relation with some of the most subtle and controverted questions of the day; but the important bearing which the acceptance of one or other of these views would have on the practice of disinfection is evident.

2. THE MEDIA IN WHICH THE CONTAGIA ARE SPREAD.

Our knowledge of this point is far more defined, and may be thus summarized:

The special and distinctive phenomena of each disease are usually attended with special implication of some part of the body, and it is especially these parts which contain the contagia. In these parts there is frequently rapid growth, and if the parts are on the surface, frequent detachment. The pus and epidermis of small-pox; the epidermis and the mouth and throat epithelium of scarlet fever; the skin and bronchial secretions of measles; the stools containing the discharged detritus of Peyer's glands in typhoid fever; the discharges of cholera; the discharges and eruptions of syphilis, glanders, farcy, and malignant pustule, are instances of this. In typhus fever the skin is greatly affected, and it is generally supposed that it is from the skin that the virus spreads, since this disorder is so easily carried by clothes; the same is the case with plague. In fact, those parts of the body which are the breeding-places of the contagious particles give off the poison in greatest amount. The portions of the body thus thrown off, and containing the contagia, may then pass into air, or find their way into water or food, and in this way be introduced by breathing, drinking, or eating, or through broken surfaces of the body.

The principles of disinfection ought evidently then to deal with the poisons at their seats of origin, as far as these are accessible to us. It was the instinct of genius which led Dr. William Budd to point out that the way to prevent the spread of scarlet fever is to attack the skin from the very first; to destroy the poison in the epidermis, or failing that, to prevent the breaking up and passage into the air of the particles of the detached epidermic scales. Oily disinfectant inunctions of the skin, and the most complete disinfection of the clothing which touches the skin of the patient, are the two chief means of arresting the spread of scarlet fever. The rules for small-pox are almost identical, though it is more difficult to carry them out. In enteric fever the immediate destruction of all particles of poison in the stools by very strong chemical reagents, and the prevention of the poison getting into sewers or drinking water or food, are the measures obviously demanded by the peculiarities of this special disease.

The more completely these points are investigated, and the more perfectly the breeding-places in the body are known, the more perfect will be our means of disinfection.

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