The bubonic plague, which is one of the most frightful diseases known, is conveyed to man by the rat and mouse.[1] Hydrophobia is usually contracted from the bite of the dog, and it is a well-known fact that this animal often harbors a minute tapeworm, a single egg of which, when swallowed by the human being, is often followed by death. Both dogs and cats probably convey diphtheria, and both unquestionably often have within their intestinal tracts tapeworms that occasionally infect children. With the exception of the rare disease known as glanders, the horse is not believed to be directly responsible for any of the maladies from which the human being suffers, but it is well established that fully 95 per cent. of house-flies hatch in the manure of these animals, and they, therefore, become indirectly responsible for some of the most serious diseases affecting the human being. It is thus seen that almost every object with which man comes in intimate contact is capable of conveying to him the poison of one or more diseases. If it were possible for us to separate ourselves completely from everything with which we are ordinarily associated there can be no question that the span of human life would be greatly increased, and that death from bacterial and parasitic diseases generally would no longer occur. All this is said not with the object of startling the reader, but to warn him of the dangers that surround him on every hand, and to urge a recognition of that which can so materially prolong his life. Fortunately these sources of infection may be almost entirely done away with by a few simple rules of life, and the health and longevity of mankind must necessarily be directly proportionate to the care with which we observe them. It is now in order to discuss in detail the subject of personal hygiene. FOOTNOTE: [1] See the volume in this Library, _Animal Competitors_, by ERNEST INGERSOLL, for the agency of rats and mice in the introduction and dissemination of plague and other diseases; and the means of destroying these pests of the farm. CHAPTER II CARE OF THE PERSON