It is thus abundantly evident that there has been a steadily increasing activity in the progress of sanitary legislation. Let us now consider what principles have become recognized, and what arc the chief sanitary improvements which have been effected or attempted.

I. Pure-Water Supply

it is universally recognized that an abundant supply of pure and wholesome water is a necessity of health. The provision of an adequate water-supply in towns is one of the most important duties of sanitary authorities, and even in the country the authorities must see that every occupied dwelling-house in the district has a sufficient and good supply within reasonable distance: they have powers to compel the provision of such where it can be done at a reasonable expense. In London an occupied house without a proper and sufficient supply of water constitutes a nuisance, and is deemed unfit for human habitation. Moreover, the standard of what constitutes a pure-water supply is tending upwards, and it is becoming recognized that chemical analysis alone is not always a sufficient test of purity. Bacteriological analysis is coming into more frequent use, and it is likely that a strict lMicteriological control of water-supplies would prove an important aid in checking the spread of disease. Koch even suggests as a standard that all filtered water containing more than a hundred microbes per cubic centimetre be discarded, but no such stringent rule is at present dreamed of in this country. The new Berlin water-supply, which is subject to strict bacteriological control, shows, as a rule, less than fifty microbes per cable centimetre. The construction and action of filtering beds is becoming better understood, and the importance of efficient filtration is well recognized.

2. Improved Sewerage

Improved systems of sewerage are to be accounted amongst the chief sanitary improvements of the past half-century. Much is due in this respect to the labours of Chad wick, who first insisted that town refuse should be removed by the scour of running water in sewers and earthenware pipes so designed and laid as to be self-cleansing. Simon considers the glazed earthenware pipe, as applied to drainage, the most valuable sanitary contrivance devised since the time of the Romans. It is clearly recognized that too great importance cannot be attached to the speedy and complete removal of all excreta and putrescible waste matters from dwelling-houses, and the ingenuity of architects and engineers has been taxed to attain this end without permitting the escape of sewer-gas into the house. It may be said that this has been attained in no small measure, and that in many of our towns the construction of the sewerage systems on modern lines has realized the dreams of Chadwick in a very successful manner. The principles which are commonly taught and accepted in sewer and drain construction include the use of impermeable materials, the employment of adequate gradients with channels of proper size (neither too large nor too small), and the adoption of efficient Hushing and ventilation. A Sanitary Authority is bound to require householders or owners to provide proper drains.

3. Scavenging

Sanely less important is the removal from dwelling-houses of such solid waste matters as cannot be got rid of by the drains - the dry refuse of the house. Sanitary authorities may, and when required by the Local Government Board must undertake scavenging duties, or contract for their efficient performance, imposing by by-law upon householders certain duties in connection therewith. Accumulations of refuse constitute a nuisance to l>e dealt with summarily.

4. Improved Construction Of Dwellings

In the matter of dwelling-houses, with which this book is more particularly concerned, very great changes and improvements have been effected. We have learned from experience and from a study of mortality statistics, the fundamental principles which underlie healthy house-construction. It is recognized that, in towns, streets must be wide and airy, the buildings not too high in proportion to the width of the streets, and with sufficient space about them to ensure a free circulation of air. Further, that thorough ventilation of houses is a necessity, that dampness of site and walls is a fertile source of disease, and that free access of direct sunlight plays an important part in the promotion of health, largely owing to its direct disinfectant action. We know that the crowding of a large population within a limited area is a powerful predisposing cause of a high death-rate, and especially of a high infant-mortality. It is admitted that the walls and roofs of houses must be of such construction and thickness as to keep out the weather and extremes of heat and cold; that the interiors must be protected not only from damp, but from the escape of sewer-gas and from exhalations from the soil, and that the apparatus for the reception and removal of solid and liquid refuse must be of such construction and situation as to prevent contamination of the air, and to ensure the removal of the refuse from the premises as speedily as possible. Not only should there be an abundant supply of pure water to every house, but. where storage of water within the house is unavoidable, it should be so stored as to<» avoid the possibility of pollution.

Amongst the wealthy classes, these principles have only to be known to be applied. The law has stepped in to compel some attention to them on behalf of the poorer classes, Its earlier attempts were more or less abortive, but the Housing of the Working Classes Act (1890) has done and is doing much good, laying, as it does, upon the Sanitary Authority the duty of proceeding against owners of insanitary premises, and of causing sanitary inspections to be made, while in Urban Districts it empowers the authority to deal with unhealthy areas. Under the Public Health Act powers are given to Urban Sanitary Authorities to make by-laws with regard to new streets and buildings, model by-laws being issued for their guidance by the Local Government Board: cellar dwellings also are placed under very strict regulations. Apart from legal obligation, public and private philanthropy has done much, both in this country and abroad, to improve the condition of the dwellings of the poor.

5. Notification Of Infectious Diseases

Among sanitary improvements having less direct bearing upon the subject of this book, two stand out prominently - the notification of infectious diseases, and the prevention of food-adulteration. The notification of infectious diseases is compulsory in London, and under local Acts in many towns: it may be adopted by any Sanitary Authority. The advantages of the practice are very obvious, since it permits of exact and immediate knowledge as to the local prevalence of any given infectious disease, and enables the requisite steps to be taken to control it.

6. Wholesome Food

The Sale of Food and Drugs Act of 1875, amended in 1879, has done much to place good and wholesome food within the reach of the poor.

7. Registration Of Plumbers

The registration of plumbers is a matter which has a very direct and important relation to sanitary house-construction. Very much depends upon the accurate and conscientious manner in which plumbing is carried out, and it is much to be desired that evidence of competency should be forthcoming on the part of those who undertake it. It is too often the case that plumbing is entrusted to men who have not the necessary skill and training to do the work as it should be done. To remedy this state of things the Plumbers' Company of London, largely on the initiative of the late Mr. George Shaw, has instituted a system of voluntary registration, which has been in practice for some years past. There is every hope that such registration will shortly become compulsory by law, and that the woes of the long-suffering householder may thereby be largely alleviated. At the same time it appears only reasonable that the man who designs and specifies the plumbing of a building, as well as the man who executes it, should give evidence of his competence.