If we view the question solely with reference to its bearing on the causation of disease, we enter a field where neither the sanitarian nor the physician is ever sure of his footing. The precise relation between bad drainage and ill-health no man knows. Certain diseases are undoubtedly traceable to conditions of air or of drinking-water due to the improper disposal of organic wastes, but the extent and exact bearing of these influences are still greatly a matter of conjecture. It is, however, undoubtedly safe to assume--and the assumption is supported by ample general observation, if not by precisely ascertained facts--that whether we are considering serious diseases or the slighter ailments, every argument leads to the enforcement of the most strenuous requirements of cleanliness. Through all the ages no one has disputed, and no one has improved upon, the simple sanitary formula, "Pure air, pure water, and a pure soil." We may safely wait until the enthusiastic investigators now engaged with the subject shall have adduced the testimony of positive facts, if we will in the mean time adhere strictly to the requirements of Hippocrates' prescription. The physician will surely not go wrong if he treats all obvious defects of drainage as positive evils, and insists upon their complete reformation. Not to confine ourselves to houses which are provided with the ordinary modern plumbing-works, but to include all collateral branches of the subject, we have to consider the following conditions: I. THE REMOVAL OF HUMAN EXCREMENT: (_a_) By water-carriage in houses provided with modern plumbing; (_b_) By some form of dry conservancy; (_c_) By the fiendish privy-vault which prevails so generally, save in the larger cities. II. THE REMOVAL OF LIQUID HOUSEHOLD WASTES: (_a_) By delivery to public sewers; (_b_) By irrigation disposal; (_c_) By delivery into cesspools. Incidentally to the above there must be considered the influences of the ultimate disposal of all household waste, whether by the public sewer or the private house-drain.