The result of a curious obtuseness to the economics of personal and domestic hygiene is also responsible for another serious dereliction of parental duty, by which health and progress have been grievously, though quite unnecessarily and constantly, hampered. I refer to the general failure to economise nervous energy or to take any interest in what is rightly called mental hygiene. Yet Press and people alike deplore the evident increase of mental abnormalities, and anticipate the future with undisguised anxiety. It has been well said that though men carry more of the wood, women carry not less of the worries of life. They _may_ in some cases escape the physical toil which strengthens; they do _not_ escape the mental toil which demoralises and kills spirit and energy if not body and health. Now, though the brain tissues do not create mental activities, nevertheless we all know that they are conditioned in some inexplicable way by that organ. Derangement in any part of the brain deranges or diminishes its functions; non-development in any part of the brain can and does arrest mind growth. Chronic over-fatigue and exhaustion, anæmia however produced, the circulation through the nervous tissues of impure blood, alter the character of the mental processes. The results of starvation may so distort them, that the horrors of the French Revolution are attributed by some authorities to this particular cause. That the imperfect lymph circulation associated with adenoid vegetations accounts for much so-called stupidity is one of the first fruits of the medical inspection of school children; that a severe shock may destroy intelligence is a fact familiar to every expert in mental hygiene. If it were generally known to parents that every impression received by this, the most sensitive of all organs, is stored up from early infancy, albeit subconsciously, and can at some future time rise up into the field of consciousness, influencing both thought and action for good or ill, a very different line of conduct would be taken towards the persons or the places which make up a young child's surroundings and most indelibly impress his brain cells.