An attempt has been made in this introductory section to enunciate the principles which underlie the construction of healthy houses, to set forth the reasons which lead up to them, and the results which may arise from their non-observance. It will be fitting to conclude with a brief summary of these principles as they apply to the sanitarian and to the householder himself. To both some knowledge of the factors causing disease and of the ways in which diseases spread is absolutely essential.

The sanitarian is concerned with the choice of a suitable site for the house, cold and damp being the two things to be avoided if possible. The proper drainage of the Bite, the exclusion of ground-air and other exhalations from the soil, and the weather-proof construction of the house itself, are all points to which he must pay attention. A due amount of air-space about the house, so that an abundance of fresh air and sunlight may gain access to it, is a condition essential to its healthiness. The internal ventilation and wanning of the house matters which must call for his utmost care, as must also the provision of an abundant supply of pure water. In this connection he must consider not only purity of source and freedom from danger of contamination by sewage, but likewise the safe and adequate storage of water within the house where such is needful. No matter must engage his more careful consideration than the system of drainage to be adopted in relation to the method of sewage-disposal which is at hand. He will be primarily responsible for the proper construction of the drains, and must insist upon good workmanship, adequate disconnection from the sewers, and proper ventilation of soil-pipes and drains, whereby the dangers of escape of sewer-gas into the house are avoided. These are the main essentials upon which the healthiness of a house depend.

But when all is done, and the householder enters into possession of his ideal premises, replete with every device which modern sanitation can suggest, he must reflect that upon him devolves the duty of keeping the house healthy. In vain will the contriver of the house have planned his efficient ventilation unless due attention be paid to it afterwards. Windows are designed to admit sunlight: pulling down the blinds may save curtains and carpets for a time from fading, but fading health is a worse evil than fading carpets. Windows are made to open, and stuffiness of rooms, and especially bedrooms, is far more likely to lead in the long run to colds and coughs than where fresh air can play freely about a room. It is scarcely too much to say that it is healthier to sleep in a draught than in a stuffy bed-room. The overcrowding of rooms, and especially of bed-rooms, is an evil carefully to be guarded against.

No house, however carefully planned, can be healthy which is allowed to become dirty. Soap and water are the main weapons with which, in conjunction with fresh air and sunlight, the householder can war against disease. His water-supply also will require vigilant attention. Most cisterns require periodical cleansing, and this should be done at least twice a year. He should understand the principles of domestic filtration, and not be content with any appliance merely because it is sold as an efficient filter. Filters can be easily tested by any bacteriologist at a small cast. However good the drains may have been when laid down, defects are liable to occur in the course of time; they therefore require periodical inspection and even testing. Moreover, accumulations of filth may occur in them: regular flushing and removal of the contents of gully holes, grease-traps, etc, should be looked to. Care also must be taken that the scavenger pays his visits with regularity and efficiency. When plumbing or other work requires to be done, the householder must remember that good workmanship is the essential requirement, and that cheap, superficial work is the least economical in the long run. Lastly, he should know what precautions should be taken in the way of isolation when infectious disease arises in his house: he should put no blind trust in any curiously-named substance sold as a disinfectant, but should know what to use and how to use it, and have reasons for the faith which is in him.

The aim of house-sanitation is to lower the death-rate and to promote the health and well-being of house-occupants. Every one has a direct interest in lowering his own death-rate and that of those dependent on him, and in living his life under conditions most conducive to health, happiness, and capacity for work. How this may be done, so far as concerns immediate external surroundings, it is the object of this book to set forth.