the injury control paradigm (AJPH, November, 1974). First, he suggests rhetorically, as if the point were beyond contention, that the health community should not be "involved in the prevention and mitigation of injury resulting from criminal acts (i.e., deliberate behavior)." Surely he does not mean to suggest that the treatment of suicide attempters and assault victims lies outside the domain of the health professions. Although primary care personnel sometimes act as if such patients were undeserving of treatment,' few are so insensitive as to openly acknowledge this bias. Secondary prevention of intentional injuries has been and will continue to be a legitimate activity of the health community. If Licht's point is that primary prevention of deliberate injuries should not become the concern of health professionals, it should be noted that there already are researchers and practitioners in suicidology, forensic pathology, and forensic psychiatry who include primary prevention of deliberate injury within the scope of their activities. Injury control researchers are well aware that "many of the general considerations relating to both injury-producing agents and injury-reducing countermeasures apply to suicide and homicide as well as to events in which injury was not in-

tended."2 Second, Licht resurrects the paralyzing belief that "Injury and the extent of injury resulting from accidents is largely a matter of chance and is difficult if not impossible to determine prior to . . . the accident." A similar view dominated thinking about illness in general for centuries. Correction of this belief is so fundamental to scientific public health that the first page of a standard textbook of epidemiology reads: "The idea that illness depends upon chance alone becomes

untenable with the knowledge that the occurrence of each type of illness follows a fairly characteristic pattern."3 And so it is with injuries: the frequency and distribution of both "accidental" and intentional injuries are as predictable as the occurrence of neoplasms. With regard to "accidents," moreover, "harmful interactions with physical agents are no more unexpected or unintentional than those involving biologic agents: A plague bacillus is as unexpected as a bolt of lightning."2 Injuries are "a matter of chance" only in the sense that they occur probabilistically, a quality which suggests to me that we work toward altering the probabilities rather than toward justifying our hazardous environment with appeals to randomness or fate. Injury control has already come of age as a paradigmatic science within preventive medicine and public health. Despite frequent assertions to the contrary, a great deal is already known about the prevention of injuries.4 In order to implement existing knowledge, however, we will have to move beyond this continuing debate over the apparent inevitability of apparently chance event.

References 1. Sudnow, D. Passing On: The Social Organization of Dying. PrenticeHall, Englewood Cliffs, NJ, 1967. 2. Baker, S. P. Injury Control. In Preventive Medicine and Public Health, Ed. 10, edited by Sartwell, P. E., Ch. 29, pp. 987-1005. Appleton-Century-Crofts, New York, 1973. 3. Fox, J. P., Hall, C. E., and Elveback, L. R. Epidemiology: Man and Disease. Macmillan, New York, 1970. 4. Dietz, P. E., and Baker, S. P. Evitable Injuries. Lancet 2:963-964, 1974. Park Elliott Dietz, MD, PhD Schools of Medicine and of Hygiene and Public Health The Johns Hopkins University Baltimore, MD 21205

INTEGRATING OPERATIONS RESEARCH AND ECONOM ICS The excellent attempt by Correa and Beasley (AJPH 64:1095, November, 1974) to integrate operations research and economics is much more important than its briefness seems to imply. However, it is not only timeeconomies that is important, but money-economies as well. The model proposed assumed a static kind of operation where personnel types were not interchangeable or replaceable by time (or money)-saving machinery or by streamlined operations. Furthermore, the model assumed that the capacity of the clinic is equal to the minimum capacity of the different types of personnel, and that the type of visits is constant through time. None of these assumptions is necessarily true. In fact, if the goal is to maximize monetary (or time) efficiency, submatrices can be incorporated into the proposed model so as to find the optimal interchange of personnel, machinery, and systems. And the capacity of the clinic is equal to the minimum capacity of the different types of personnel only if all of the operations are in series and none are in parallel. And the type of visits may change with time, as from flu "a" to flu "b." Therefore, when efficiency exceeds 100 per cent, it does not necessarily mean that the time used to attend patients is below the minimum

acceptable. 0. B. Kaplan, PhD, MPH, RS Department of Environmental Health Services San Bernardino County, CA

LETTERS TO THE EDITOR

185