_How Disease Germs Grow_.--Experiments having shown that no life is known to spring from inanimate matter, we may reasonably suppose that just as wheat does not grow except from seed, so no disease occurs without some disease germ to produce it. Then, again, we may logically assume that each disease is due to the development of a particular kind of germ. If we plant smallpox germs, we do not reap a crop of scarlatina or measles; but, just as wheat springs from wheat, each disease has its own distinctive germs. Each comes from a parent stock, and has existed somewhere previously....Under ordinary circumstances, these germs, though nearly always present, are comparatively few in number, and in an extremely dry and indurated state. Hence, they may frequently enter our bodies without meeting with the conditions essential to their growth; for experiments have shown that it is very difficult to moisten them, and till they are moistened, they do not begin to develop. In a healthy system they remain inactive. But anything tending to weaken or impair the bodily organs, furnishes favorable conditions, and thus epidemics almost always originate and are most fatal in those quarters of our great cities where dirt, squalor, and foul air render sound health almost an impossibility.... Having once got a beginning, epidemics rapidly spread. The germs are then sent into the air in great numbers, and in a moist state; and the probabilities of their entering, and of their establishing themselves even in healthy bodies, are vastly increased....Climate and the weather have also much influence on the vitality of these germs. Cold is a preventive against some diseases, heat against others. Tyndall found that sunlight greatly retarded and sometimes entirely prevented putrefaction; while dirt is always favorable to the growth and development of germs. _Sunshine and cleanliness are undoubtedly the best and cheapest preventives against disease.--"Disease Germs" Chambers's Journal_.