Disease Germs. In all foul air there are scores of different kinds of germs--many of them comparatively harmless, like the yeasts, the moulds, the germs that sour milk, and the bacteria that cause dead plants and animals to decay. But among them there are a dozen or more kinds which have gained the power of living in, and attacking, the human body. In so doing, they usually produce disease, and hence are known as _disease germs_. [Illustration: DISEASE GERMS (Greatly magnified) (1) Bacilli of tuberculosis; (2) Bacilli of typhoid fever.] These germs--most of which are known, according to their shape, as _bacilli_ ("rod-shaped" organisms), or as _cocci_ (round, or "berry-shaped" organisms)--are so tiny that a thousand of them would have to be rolled together in a ball to make a speck visible to the naked eye. But they have some little weight, after all, and seldom float around in the air, so to speak, of their own accord, but only where currents of air are kept stirred up and moving, without much opportunity to escape, and especially where there is a good deal of dust floating, to the tiny particles of which they seem to cling and be borne about like thistle-down. This is one reason why dusty air has always been regarded as so unwholesome, and why a very high death rate from consumption, and other diseases of the lungs, is found among those who work at trades and occupations in which a great deal of dust is constantly driven into the air, such as knife-grinders, stone-masons, and printers, and workers in cotton and woolen mills, shoddy mills, carpet factories, etc. [Illustration: A VACUUM CLEANER Most of the dust being emptied from the bag, would, in ordinary sweeping, have been merely blown around the room. By the vacuum process the dust is sucked up through the tube into the storing receptacle.] In cleaning a room and its furniture, it is always best to use a carpet sweeper, a vacuum cleaner, or a damp cloth, as much as possible, the broom as little as may be, and the feather duster never. The two latter stir up disease germs resting peacefully on the floor or furniture, and set them floating in the air, where you can suck them into your lungs. There are three great groups of disease germs which may be found floating in the air wherever people are crowded together without proper ventilation--for most of these disease germs cannot live long outside of the body, and hence come more or less directly from somebody else's lungs, throat, or nose. The most numerous, but fortunately the mildest group, of these are the germs of various sorts which give rise to _colds_, _coughs_, and _sore throats_. Then there are two other exceedingly deadly germs, which kill more people than any other disease known to humanity--the bacillus of consumption, and the coccus of pneumonia.