Practical success in sanitation is impossible without the recognition of mind, both in the actual working of the organs of the living body and in the knowledge and acceptance by mankind of the conditions which are essential to health. If the human constitution be governed by laws in obedience to which healthy growth is alone possible, then those laws must be carefully sought for before we can build up a science of hygiene. To regard living beings as simply material bodies, without the constant and varying influences of mental action upon the working of those bodies, is an intellectual error which disregards the essential condition of mental harmony in relation to health. It must also be recognised that whatever may be the discoveries of physiological science, they will remain barren unless applied by individuals. In all the concerns of life, whether in the application of principles or in the unconscious formation of habits, we are compelled to deal with the ceaseless power or effect of Will. To treat even the most ignorant adults by arbitrary, unreasoning compulsion is a scientific blunder.[3] _The Two Problems of Hygiene._--The two fundamental questions for hygiene to solve are therefore: 1st. What are the conditions of healthy growth? 2nd. How can those conditions be secured? In answering these two fundamental questions the problem of mental action enters into every hygienic section of a Congress, and is the keynote which must be struck if harmony of theory and practice is to be attained. But in consequence of too narrow a view of hygiene these questions were not solved, and this remarkable assembly of learned men, brought together with such careful preparation and hospitable welcome, produced no practical results of the commanding value that the public had a right to expect from it. Sanitary legislation was shown to be largely evaded, but the reasons for this unsatisfactory evasion were not examined; the results of experimental research were proved to be strangely contradictory, but the conditions which would harmonize them were not discovered; unproved theories abounded, but the fallacies that vitiated them were not made clear. Disappointment as to the practical utility of the Congress was widely felt both at home and abroad. This disappointment with the results of the Congress has been publicly expressed by our foreign guests. A clever abstract of the work done at this Seventh International Hygienic Congress has been published in Paris by the well-known editors of _The Review of Hygienic and Sanitary Police_. Some noteworthy statements are made in the introduction to this volume which should be seriously considered by all who reverence righteous sanitary science as the foundation of human welfare, but who also know that sanitary science must approve itself to the good sense of a people, or it will be of little practical utility.