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much greater had it not been for the flight of the population." Now, all this fearful havoc was traced to the water from the pump in question, and affixed to it by a chain of evidence most complete, the witness to it being not only the fact of persons drinking the water being seized by cholera, but cases of immunity, such as that of a brewery in the centre of the district, the seventy men employed in it never taking the pump water, and all, without exception, escaping the infection. There were also other striking instances of persons who lived out of the district contracting this disease, but who had managed to obtain some of the water.
Dr. Simon has shown that in London the houses supplied with water drawn from the river, polluted with sewage, furnished a death-rate from cholera of 13 per 1,000; while in other houses, situated in quite similar circumstances, sometimes only on the opposite side of the street, but supplied with pure water, the rate was only 37 per 1,000. Similar evidence is given with respect to Koenigsberg and Berlin. Dr. Buchanan's diagram, showing the results of improved drainage and water supply, also testifies to the influence of these reforms in preventing cholera. But none of these instances exclude the possibility of other influences being at work, and we have a strongly-expressed opinion from Professor Pettenkofer that the true cholera poison is not rendered virulent by water, but by the soil. He believes that the only influence that drinking water can have on the spread of the disease is by acting as a means of conveyance of the germs engendered and hatched elsewhere. There must doubtless be an original source for the poison in some cases of cholera; he does not suppose that it can be formed de novo out of soil, and he admits that it only spreads by human intercourse. But cholera, like typhoid fever, is certainly not very contagious from person to person, and Professor Pettenkofer believes that the quality that renders it virulent is generally, if not always, found in the soil; and in order that this may have its full effect there must be a certain degree of warmth and dampness, and this latter condition is best fulfilled when the ground water subsides suddenly after a previous rise. A porous soil, into which the specifically infected filth can sink, is therefore the most dangerous.
The evidence upon which this theory rests is certainly very strong, though, as we shall see presently, it does not confirm Pettenkofer's views as to the exclusive influence of the soil. Thus, in Bavaria, the theory was submitted to a commission of enquiry as
to the distribution of cholera, and it was found to be, indeed, true that all the places infected by cholera were places on porous soil, and in certain villages in mountainous districts, which appeared at first sight to be exceptions to the above rule, it was discovered that the disease arose where the houses were built upon clefts in the rocks filled up with alluvial soil.
At Buda-Pesth, it is stated by Foder that the cholera mortality rises and falls inversely with the ground water, increasing as the water declines, and lessening with its rise; and a similar observation was made by Messrs. Lewis and Cunningham in an outbreak of cholera at Calcutta in 1873-74. In the cholera epidemic of 1854 Dr. Farr noted the fact that one large district in London, built on gravel, was severely visited by cholera, but that an institution, built upon a sort of island of brick clay, in the midst of it, was entirely exempt. There are, however, few rules without exceptions, and that filth alone, without soil, is quite capable of nourishing cholera may be shown by the fact that during the first visitation of cholera in England one of the places which suffered most severely, owing to its filthy local conditions, was Megavissey, on the granitic formation in Cornwall. (Galton's "Healthy
Houses," p. 21.) Moreover, Dr. B. W. Richardson (Trans. Epid. Soc., vol. ii.) points out that in the Crimea certain ships supplied with distilled water were exempt from the disease, with one exception, and in this instance the water had passed through a foul hose-pipe.
It will be useful, however, to bear in mind the possibility that certain diseases, such as typhoid fever and cholera, may have their virulence intensified by contact with the organic matter of soils, and in this regard it may be interesting to recall Dr. Thiersch's observation that "cholera stools develop a special activity after being kept for from two to six days," an observation confirmed by an English physiologist, Dr. Burdon Sanderson. It is well known also that linen soiled by the discharges is especially infective and that washerwomen often fall victims to the disease.
II. Another disease that is undoubtedly fostered by dampness in the soil is consumption. In the year 1862, Dr. Bowditch, of Massachusetts, made an elaborate series of enquiries as to the causes of consumption. Questions were addressed to medical men in all parts of the country upon much the same plan as that now adopted by the Collective Investigation Committee of the British Medical Association, and as a result of these inquiries, be
came to the conclusion that-(1) "A residence on or near a damp soil, whether that dampness is inherent in the soil itself or caused by percolation from adjacent ponds, from marshes, or springy soils, is one of the primal causes of consumption in Massachusetts, probably in New England, and possibly in other portions of the globe. (2.) Consumption can be checked in its career, and possibly, nay probably, prevented by attention to this law."
Shortly afterwards, and without any knowledge of Dr. Bowditch's conclusions, Dr. Buchanan, who is now the chief medical officer to the Local Government Board, came to much the same conclusions as the result of an elaborate research into the distribution of consumption in the three south-eastern counties of England beyond the limits of the Metropolis.
His conclusions are well worthy of being quoted in extenso— they are as follow:
(1.) Within the counties of Surrey, Kent, and Sussex, there is, broadly speaking, less phthisis (ie., consumption) among populations living on pervious soils than among populations living on impervious soils.
(2.) Within the same counties there is less phthisis among popuations living on high-lying pervious soils than among populations living on low-lying pervious soils.
(3.) Within the same counties there is less phthisis among populations living on sloping impervious soils than among populations living on flat impervious soils.
(4.) The connection between soil and phthisis has been established in this enquiry-(a) by the existence of general agreement in phthisis mortality between districts that have common geological and topographical features of a nature to affect the waterholding quality of the soil; (b) by the existence of general disagreement between districts that are differently circumstanced in regard of such features; and (c) by the discovery of pretty regular concomitancy in the fluctuation of the two conditions, from much phthisis with much wetness of soil, to little phthisis with little wetness of soil. But the connection between wet soil and phthisis came out last year in another way, which must here be recalled (d) by the observation that phthisis had been greatly reduced in towns where the water of the soil had been artficially removed, and that it had not been reduced in other towns where the soil had not been dried.
(5.) The whole of the foregoing conclusions combine into one-which may now be affirmed generally, and not only of particular districts-that "wetness of soil is a cause of phthisis to the population living upon it."
(6.) No other circumstance can be detected, after careful consideration of the materials accumulated during this year, that coincides on any large scale with the greater or less prevalence of phthisis, except the one condition of soil.
Good drainage has been found to diminish the prevalence of the disorder by as much as 50 per cent. These results have since been confirmed by Dr. Haviland, and by the Registrar-General of Scotland. In the conclusions drawn from his map of the distribution of phthisis in England and Wales, Dr. Haviland says: "Damp, clayey soil, whether belonging to the wealdon, oolitic, or cretaceous formation, is coincident with a high mortality;" and the Registrar-General, in his seventh report, remarks that "the towns, villages, hamlets, or houses which were situated at or near undrained localities, or were on heavy, impermeable soils, or on low-lying ground, and whose sites were consequently kept damp, had a very much larger number and proportion of cases of consumption than towns, villages, hamlets, or houses which were situated on dry or rocky ground, or on light porous soils, where the redundant moisture easily escaped."
It is evident from all this evidence that there is some close relationship between the condition of the soil and consumption; but how a damp subsoil can increase the prevalence of the disease is not so clear. Whether it is by simply increasing the tendency to colds and bronchitis, which are frequently the precursors of tubercular disease, or by directly fostering the germs of the disease itself. It is now known that the immediate cause of consumption is another of the small organisms, a bacillus similar to those associated with typhoid fever and cholera. But it can hardly be a sojourn in damp soil that promotes the growth of this particular bacillus of tubercle. Prof. Koch, who discovered it, has shown that it cannot be cultivated except between the temperatures of 86° and 107° Fahr., and these temperatures are far higher than any that we have in the soil of this country. It must then be in some indirect fashion that the soil affects the prevalence of the disease; and it is not unreasonable to conclude that the increased tendency to catarrhs on damp soil has something to do with the result. But there are probably other influences also at work.
The vapours that arise from damp ground, and which we have seen to make their way into houses, are often very impure, and charged with organic matter that may be a suitable food for the tubercle bacillus; and in most houses there are warm nooks where there would be sufficient heat to hatch them into activity.
Whether this is the true explanation of the connection between dampness of soil and consumption or not, it is certain that although the disease is not infectious in the ordinary sense, it may be introduced into houses and places where it had not previously existed, and therefore we cannot ascribe the promotion of the disease solely to the influence of "catching cold."
The following cases recorded by the Collective Investigation Committee are sufficiently significant on this head.
(1.) "In 1862 a servant came home to her mother (a widow, with three sons and two daughters, all grown up, father died of epithelioma) suffering from phthisis. The house, consisting of two rooms and an attic, and lying under the brow of a hill, on its northern aspect, was ill-ventilated and worse lighted. By the end of 1868 the only survivor of this family, she being still alive and healthy, was a thin delicate girl, who took little or no part in the nursing. They all died of phthisis, the mother dying last between fifty and sixty years of age.'
(2.) "A young man, of the Indian navy, came home suffering from phthisis. In a few months two of his sisters were taken with the same complaint and died. A third sister married and soon afterwards died of the same disease. The young man also died. Later on the father was similarly affected and died. After his death the widow became phthisical and died also. I should think four years covered the whole outbreak, that is, from the arrival of the son from India. The father was originally a very healthy, strong man, and all the children healthy up to about twenty or twenty-one, or even later; one sister still lives, and is now between forty and fifty."
In these cases truly something seems to have been introduced from without into dwellings previously untainted by the disease. 12. There are yet other diseases whose fatality, at any rate, is increased by the condition of the soil, especially by dampness of the soil.
Dr. Blaxall in a recent report gives an interesting proof of this statement. He is comparing two parts of the same town, Swindon. Old Swindon, situated on limestone and sand, is at an