“It has been long known that, with increase of years, up to that period of life which has been denominated the second childhood, the human constitution becomes gradually more resistful, and as it were slowly hardened against the repeated attacks of those more acute disorders, incident to an inferior degree of sanitary civilisation, by which large portions of an infant population are continually overcome and rapidly swept away. From the operation of these and more extraneous influences of a disturbing character, an infant population is almost entirely exempted; and on this account it is considered that an infant population constitutes, as it were, a delicate barometer, from which we may derive more early and more certain indications of the presence and comparative force of local causes of mortality and disease than can be obtained from the more general methods of investigation usually pursued.” The above evidence is confirmed by Mr. Toynbee:— “The disease of hydrocephalus, of water in the brain, so fatal to children, I find associated with symptoms of scrofula, and arising in abundance in these close rooms. I believe water in the brain, in the class of patients whom I visit, to be almost wholly a scrofulous affection.” {116b} But supposing people aware of the necessity for good air, and therefore for ventilation, what is to be done? In houses in great towns certainly, and I should say in all houses, some of the care and expense that are devoted to ornamental work, which when done is often a care, a trouble, an eyesore, and a mischief, should be given to modes of ventilation, {117a} sound building, abundant access of light, largeness of sleeping-rooms, and such useful things. Less ormolu and tinsel of all kinds in the drawing-rooms, and sweeter air in the regions above. Similar things may be done for and by the poor. {117b} And it need hardly be said that those people who care for their children, if of any enlightenment at all, will care greatly for the sanitary condition of their neighbourhood generally. At present you will find at many a rich man’s door {117c} a nuisance which is poisoning the atmosphere that his children are to breathe, but which he could entirely cure for less than one day’s ordinary expenses. I am afraid that ventilation is very little attended to in school-rooms, either for rich or poor. Now it may be deliberately said that there is very little learned in any school-room that can compensate for the mischief of its being learned in the midst of impure air. This is a thing which parents must look to, for the grown-up people in the school-rooms, though suffering grievously themselves from insufficient ventilation, will be unobservant of it. {118} In every system of government inspection, ventilation must occupy a prominent part.