All these branches are so closely related that it is impossible to mark any exact dividing-line. But, in a general way, there is a broad distinction between eugenics, which is the hygiene of future generations, and the other two, which relate to the present generation, as also between these two themselves. Thus public hygiene is that which is practised by the government for its citizens, while individual hygiene is that which is practised by the citizens for themselves. Public hygiene consists chiefly in efforts by the government to maintain a wholesome environment in which to live, including good outdoor air--without smoke or foul odors--clean streets, pure water, good sewers, quarantine, and legal regulations concerning houses, schools, prisons, hospitals, and other public institutions, foods sold in markets, and conditions of employment. It is chiefly useful in preventing _acute_ or infectious diseases, such as typhoid fever, scarlet fever, measles, whooping-cough, small-pox, yellow fever, and diphtheria, and in preventing accidents and occupational diseases. Individual hygiene is chiefly useful in preventing the _chronic_ or degenerative diseases, that is, diseases of nutrition and of circulation, such as heart and kidney affections, nervous prostration, insanity. Public hygiene has made much progress during recent years. In consequence, the number of deaths from the acute or infectious diseases has been greatly diminished. Health officers are beginning to demonstrate the truth of Pasteur's words, "It is within the power of man to rid himself of every parasitic disease." It is this work which has reduced the general death-rate in civilized countries and sometimes cut it in two, as at Panama. The United States Public Health Service, on invitation of the Peruvian Government, recently cut the death-rate in two in one of Peru's disease-ridden cities. Individual hygiene, on the other hand, has been greatly neglected, especially in the United States, and, doubtless largely as a consequence, the death-rates from the chronic or degenerative diseases are increasing rapidly. A further consequence is that, in the United States, while the death-rate in the early years of life (when infectious diseases do most of the killing) has been decreasing, the death-rate in later life (when the chronic diseases do most of the killing) is increasing. In Sweden, on the other hand, where individual hygiene is more generally applied, the death-rate is declining at all times of life. (See "Signs of Increase of the Degenerative Diseases," SUPPLEMENTARY NOTES.) Both public and individual hygiene are being invoked in the fight against tuberculosis, a disease at once infectious and chronic, due to germs and to wrong methods of living. [Sidenote: Cooperation Necessary]