regard to the spread of cholera and enteric fever become so important, for he insists on humidity of soil as a necessary factor in the etiology of any localised outbreak of either disease.

An undrained or damp state of soil, especially in populous places, is thus fully proved to be highly inimical to public health, and, according to Mr. Simon, it answers to the legal definition of the term "nuisance." Sanitary authorities are therefore "bound to provide that such a state shall not continue through want of proper constructions for the drainage."

SECTION II. SANITARY ASPECTS OF THE WATER

CARRIAGE SYSTEM OF EXCRETAL REMOVAL.

So much has already been said with regard to the evils resulting from collections of excretal matter in towns, that, at first sight, the superiority of any system which prevents these accumulations would appear to be placed beyond dispute. Unfortunately, however, the sewer-system is by no means free from serious dangers, and these have at times been attended with such disastrous consequences that many have been led to condemn it altogether. But an examination of a few of the more important outbreaks of disease, which have been attributed to the introduction of sewers, will show that such wholesale condemnation is groundless; that in fact such outbreaks are due to faults in the system, and not to the system itself. Thus, in the first inquiry of Dr. Buchanan, already alluded to (Ninth Report of the Medical Officer to the Privy Council), it was found that at Chelmsford the death-rate from enteric fever had increased, since the introduction of the sewer

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At

system, 5 per cent, and at Worthing it had increased 23 per cent. In both these places, however, there was backing up of the sewage, and, as a consequence, the sewer-gases were forced up into the houses. Chelmsford, the sewage was received into a tank or underground well; and, at times, when the pumpingengine was not at work, the well filled, and choking of the outfall-sewer, and flooding of the cellars, ensued. At Worthing, again, although there was not so much backing up of the sewage, there was no provision made for ventilation; and hence, in the outbreak of 1865, the disease "almost exclusively attacked the well-to-do occupants of houses on the higher levels, where the water-closets were inside the houses, and almost entirely spared the houses, mostly of a much poorer sort, situated on lower levels, where the closet was placed outside the house. It was not so in the times of cesspools; then these low-lying poor houses were far more attacked with fever than the others." At Morpeth it was also observed that occasional outbreaks of enteric fever had followed times of flood, during which the outfall sewer was under water.

But

Other instances of a similar character might easily be multiplied, but these are sufficient to show that all such outbreaks are due either to faulty construction, deficient ventilation, or imperfect flushing of sewers, or to backing up of sewage in low-lying towns. while outbreaks of enteric fever do occasionally take place through the agency of sewers, there was no point more clearly established in the whole of Dr. Buchanan's inquiry, than the remarkable reduction of the death-rate from this disease which had taken place in almost all the towns where a system of sewerage had been carried

out. Thus, in nine of the twenty-five towns examined, the diminution in the number of deaths was over 50 per cent, and in ten others from 33 to 50 per cent, the average reduction being about 45 per cent. The same

kind of evidence is also afforded in the account of the sanitary condition of Liverpool, given by Dr. Trench in 1868. Dr. Trench writes:-In 1868 "there raged a widespread epidemic of typhoid fever in the town, and in the rural districts of the town. . . . While in the families of the rich, in their costly suburban dwellings, there was raging a fever, clearly and unmistakably due to the pestiferous emanations from ill-drained cesspools, or other collections of filth or decomposing organic matter; the districts in the borough of Liverpool known as the fever districts, and wherein no midden-steads or cesspools were allowed by the Council to remain unaltered, continued, during the whole period of the epidemic, remarkably healthy, and free from fever."

As regards other diseases, it appears that cholera epidemics had been "rendered practically harmless" in all of the twenty-five towns examined by Dr. Buchanan ; and in the majority of cases the death-rate from diarrhoea had also been considerably reduced. Moreover, the general death-rate was lowered in some towns over 20 per cent; and the progress made by the inhabitants in cleanliness, decency, and self-respect, was found to be as striking as the improvement in their health measured by the mortuary returns. No doubt, the improved water-supply, which was generally obtained at the same time, aided in the common health-amelioration, but there can be little question that the system of excretal removal by water-closets and sewers was the real agent at work.

SECTION III-SANITARY ASPECTS OF

SEWAGE IRRIGATION.

It has already been shown in the previous chapter that irrigation is the only method of sewage disposal which sufficiently purifies the sewage, and, at the same time, secures a profitable agricultural return. It now remains to be seen whether the carrying out of the system is attended with danger to public health, And here it may be premised that the same difficulty is encountered in sifting evidence as throughout the whole sewage-question, the difficulty, namely, of dealing with sweeping generalisations which have been based on isolated or exceptional cases. For while, on the one hand, it appears that Dr. Letheby and others condemn all sewage farms as pestilential swamps, Dr. Carpenter of Croydon and other strenuous advocates of the system, so far from pronouncing them as in any way dangerous to health, maintain that the general health of the neighbouring inhabitants is actually improved by them. But this is pushing the argument perhaps too far on both sides. No doubt some sewage farms answer to Dr. Letheby's description, especially such farms as have been laid out, without any due regard to drainage, in low-lying districts, and those that have been planned on the "catch-water" system. It is evident that this latter system necessitates a swampy condition of both soil and subsoil, inasmuch as the sewage passes over successive areas of land, overflowing from each into a "catch-water" ditch, which conveys it to the next. Again, when the sewage is not delivered in a fresh state, and at least properly strained, if not disinfected by some precipitation process, offensive

emanations are undoubtedly given off, and may become productive of serious disease. But though all this is perfectly true, it is no argument against the system when properly carried out, unless direct evidence can be brought forward to show that, even when the engineering and management are alike satisfactory, there is not only possible but actual risk to health. Such evidence, however, does not appear to be forthcoming; and even with regard to farms which have neither been planned nor are conducted according to the most approved principles, the evidence as regards the production of disease is of a negative character. Thus, Sir Robert Christison testifies concerning the Craigentinny Meadows, near Edinburgh "I am satisfied neither typhus, nor enteric fever, nor dysentery, nor cholera, is to be encountered in or around them, whether in epidemic or non-epidemic seasons, more than in any other agricultural district of the neighbourhood."

(First Report At Norwood,

of the Rivers Pollution Commissioners.) again, where the farm lies on a deep clay soil, Dr. Cresswell states that the health of the neighbouring inhabitants is in no way influenced by it; and according to the Ninth Report of the Medical Officer of the Privy Council, the irrigation works at Worthing do not cause any description of nuisance or injury to health. So far, therefore, the production of disease arising from fæcal pollution of air or water by the system, when properly managed, is not substantiated. But it was feared at one time that entozootic diseases would be greatly propagated, no matter how efficiently the system might be carried out, and Dr. Cobbold's high authority gave currency to the belief. Dr. Cobbold, however, with rare scientific candour, and after