Until recently the most reliable test of health rights not enforced was the number of cases of preventable, communicable, contagious, infectious, transmissible diseases, such as smallpox, typhoid fever, yellow fever, scarlet fever, diphtheria, measles, whooping cough. By noticing streets and houses where these diseases occurred, students learned a century ago that the darker and more congested the street the greater the prevalence of fevers and the greater the chance that one attacked would die. The well-to-do remove from their houses and their streets the dirt, the decomposed garbage, and stagnant pools from which fevers seem to spring. It was because fevers and congestion go together that laws were made to protect the well-to-do, the comfortable, and the clean against the slum. It is true to-day that if you study your city and stick a pin in the map, street for street, where infection is known to exist, you will find the number steadily increase as you go from uncongested to congested streets and houses, from districts of high rent to districts of low rent. Because it is easier to learn the number of persons who have measles and diphtheria and smallpox than it is to learn the incomes and living conditions prejudicial to health, and because our laws grant protection against communicable diseases to a child in whatever district he may be born, the record of cases of communicable diseases has heretofore been the best test of health rights unenforced. Even in country schools it would make a good lesson in hygiene and civics to have the children keep a record of absences on account of transmissible disease, and then follow up the record with a search for conditions that gave the disease a good chance. But to wait for contagion before taking action has been found an expensive way of learning where health protection is needed. Even when infected persons and physicians are prompt in reporting the presence of disease it is often found that conditions that produced the disease have been overlooked and neglected.