Of the bacteria and similar microscopic germs of disease--to which all our infective fevers are due--we have only become aware quite recently, within the half-century. Before they were known, cleanliness and the destruction of putrescible matter in man's surroundings had, it is true, been urged by sanitary reformers. Disinfectants and antiseptics were deliberately made use of for this purpose in the mid-Victorian period, when carbolic acid and chlorinated lime were established in the place of those feebler destroyers of the germs of putrefaction and disease--namely, the extracts of aromatic herbs or the essential oils themselves. These, as perfumes and unguents, really served, not merely to gratify the olfactory sense, but to destroy by their chemical action the germs of disease. Men tolerated gnats and their bites (mosquitoes as we prefer to call them in order to delude ourselves into the belief that they are not British) until it was discovered that they, and they only, carry the parasitic germs of two deadly diseases--malaria, or ague, and yellow fever. Now we shall destroy the pools in which they breed, just as we are destroying the manure heaps in which the house-fly breeds. When we look over the list it is really astonishing how much remains to be done, even in England, in establishing increased cleanliness and freeing ourselves from the murderous tyranny of parasites. It is a simple but horrible fact that the poorest class in our big cities still swarms with vermin. And not only are the poor in great cities thus afflicted. The recent compulsory medical inspection of school children has shown that in some of the smiling rural districts of England 80 per cent. of the children have lice in their heads. Everyone should help to gain further cleanliness and freedom from this form of oppression.