It would perhaps be difficult to cite any very significant improvements in public health until within the past two hundred years. Quarantine procedure, attributed to the mediaeval Italians, must, in its original form, have been an uneconomical and dubiously efficient measure. It consisted in holding the personnel of suspectedly infected vessels on board for forty days before permitting landing. It was assumed that by this time all the susceptibles would be dead or recovered.

The past two centuries, however, have been characterized by very rapid progress in both knowledge and practice. Edward Jenner in 1798 laid the basis for the control of smallpox, a disease which in his day disfigured or blinded most of the population whom it did not kill. Specific immunization, therefore, commonly regarded as among the most recent weapons against disease, was really among the first to be rationally and widely applied. The epidemiological approach, also, whose modern revival with improved technic is often mistaken for its beginning, was successful during the middle of the nineteenth century in devising adequate, if cumbersome, methods of control of both typhoid fever and Asiatic cholera. Various poisons, apt to affect large groups - lead, arsenic, ergot - were also detected, and rational means for their control were devised. In nutritional disease nothing important was discovered until about the beginning of this century, with the exception of the significant fact that scurvy could be prevented and cured by feeding fruit juice or fresh vegetables. The mere classification of foods into their caloric content, useful enough in its way, ignored the much more significant content in vitamin, the discovery of which has revolutionized our notions of nutrition. The fact of infestation with certain animal parasites was recognized, but little was done to prevent it. On the social side, health organizations began to be established as it became apparent that something could be done in a governmental or community way to control at least some of the worst of the besetting diseases.

This very brief and cursory review brings us up to the period of the discovery of bacteria and their important role in the causation of sickness. Far more important for humanity than the demonstration of the bacterial cause of this or that particular disease, was the generalization by Pasteur that germs do not originate spontaneously, but are always the offspring of antecedent organisms of the same kind. It is on this generalization that one important branch of present-day public health work is based. Obviously, if germs could originate spontaneously in filth, water, or soil, their control would be virtually impossible. On the other hand, if they came only from ancestors in kind, these having their common habitats in the bodies of persons sick with particular and recognizable diseases, something might be done to prevent their spread to those who are well.

Public health work has had different beginnings in various environments. In England, for example, it is said to have originated in social reform. The abuses in working conditions and housing, arising from rapid and uncontrolled industrial changes, aroused the nation to the passage of legislation which, although aimed at the abuses, actually had the effect of public health acts. Typhus fever in New York, erroneously believed to be due to filth as such, led to the establishment of a health department and a campaign of sanitation. In Panama public health work was undertaken as an essential preliminary to building the canal. Elsewhere the work has been the outgrowth of hospital activities, of charitable efforts, of missionary endeavor, or of business enterprise. Sooner or later, however, it tends to become a function of government, the reasons for this being chiefly that in some of its aspects the exercise of police powers becomes necessary, and that the fixing of responsibility cannot be satisfactorily secured under other auspices.

In the United States the general order of establishment of governmental agencies for carrying out public health work has been: first, the large cities; second, the states; third, the small cities; fourth, the counties; lastly, the villages. The Federal Government under our Constitution can function only in international and interstate activities, but in these it finds a large and useful field. Public health duties have been assigned to it for only about half a century, but in one way or another it has contributed to the cause of public health for a much longer time.

The systems of organization which have been developed in different parts of the world for carrying out public health work still vary widely. In some countries the national government exerts a strong influence through its representatives, even down to the smallest communities. In others the central health office is little more than a supervising and recording device and a purveyor of safe water; the measures are carried out largely by private physicians throughout the land. The measures themselves, however, are found to be very similar in countries of comparable geographic and cultural status. This latter fact is of course traceable to the general adoption of scientific methods in public health work. If based on tradition or mere speculation, public measures would of course vary extensively according to local influences.

In common with other human activities, public health work has undergone a progressively widening interpretation as to scope. Originally confined largely to dealing with only the most devastating pestilences, it became applied later to those diseases which we have always with us and, for that reason, are prone to disregard, but which in the aggregate are far more destructive than so-called epidemics. The unusual, the exotic, the sensational, create a public demand for action, which the insidious and commonplace do not. As long as disease was regarded as largely a matter of filth, public health endeavor was directed chiefly toward cleaning up visible accumulations of refuse and rubbish. To this sort of activity the term sanitation still clings. To a considerable portion of the public this is still the beginning and end of public health work. They call upon the health office to abate nuisances, but do not seek or follow its advice on matters of greater importance to their welfare.