Other Diseases.--Many other diseases have been traced to bacteria. Diphtheria is one of the best known. As it is a throat disease, it may easily be conveyed from one person to another by kissing, putting into the mouth objects which have come in contact with the mouth of the patient, or by food into which the germs have been carried. Another disease which probably causes more misery in the world than any other germ disease is syphilis. Hundreds of thousands of new-born babies die annually or grow up handicapped by deformities from this dread scourge. Syphilis and gonorrhea, both diseases of the same sort and contracted in the same manner, hand down to innocent wives and still more innocent children a heritage of disease "even unto the third and fourth generation." Grippe, pneumonia, whooping cough, and colds are believed to be caused by bacteria. Other diseases, as malaria, yellow fever, sleeping sickness, and probably smallpox, scarlet fever, and measles, are due to the attack of one-celled animal parasites. Of these we shall learn later in Chapter XV. Immunity.--It has been found that after an attack of a germ disease the body will not soon be again attacked by the same disease. This immunity, of which we will learn more later, seems to be due to a manufacture in the blood of substances which fight the bacteria or their poisons. If a person keeps his body in good physical condition and lives carefully, he will do much toward acquiring this natural immunity. Acquired Immunity.--Modern medicine has discovered means of protecting the body from some contagious diseases. Vaccination as protection against smallpox, the use of antitoxins (of which more later) against diphtheria, and inoculation against typhoid are all ways in which we may be protected against diseases. Methods of fighting Germ Diseases.--As we have seen, diseases produced by bacteria may be caused by the bacteria being _directly_ transferred from one person to another, or the disease may obtain a foothold in the body from food, water, or by taking them into the blood through a cut or a wound or a body opening. It is evident that as individuals we may each do something to prevent the spread of germ diseases, especially in our homes. We may keep our bodies, especially our hands and faces, clean. Sweeping and dusting may be done with damp cloths so as not to raise a dust; our milk and water, when from a suspicious supply, may be _sterilized_ or pasteurized. Wounds through which bacteria might obtain foothold in the body should be washed with some _antiseptic_ such as carbolic acid (1 part to 25 water), which kills the germs. In a later chapter we shall learn more of how we may cooperate with the authorities to combat disease and make our city or town a better place in which to live.[23]