(6), Aycock (7), Turner and Young (8), and Sabin (9). The main issues and controversial findings will be summarizedi however, to indicate how they determined the design of the present study.Tests with strains of poliomyelitis virus which had undergone many passages in monkeys ("MV," "A ycock," or others) (1-7) or in mice (Lansing) (8,(10)(11)(12)(13)(14)(15) invariably gave a similar pattern, which varied only quantitatively in different investigations. The sera obtained during the acute stage of the disease either had no antibody and, with certain exceptions, developed none during convalescence, or else neutralized the virus and, when tested quantitatively, only rarely increased in titer during convalescence. (1, 2, 4-7, 16, 17) especially when the virus and the patients were derived from the same outbreak, yielded different results in different investigations. Thus, Paul and Trask (1), Howitt (16), Kessel, Stimpert, and Fisk (6), and Aycock (7) reported that a considerable number of patients' convalescent sera which failed to neutralize standard, laboratory, multiple-passage virus possessed antibodies for a strain of virus recovered during the same outbreak from which the patients were derived. Using these freshly isolated strains, it was occasionally possible to demonstrate absence of antibody in the serum obtained during the acute phase of the illness and presence during convalescence, when similar tests with the multiple-passage, laboratory strains either revealed no difference or yielded negative results. On the other hand, Brodie, Fischer, and StiUerman (4) and Burnet and Jackson (5) found no difference in the results of the neutralization tests with "standard" laboratory strains as compared with virus recovered during the same outbreak from which their patients were derived. The difficulties in appraising these data, which were appreciated by many of the investigators, stemmed from one or more of the following circumstances:
Tests with strains of poliomyditis virus of recent human origin(a) the tests carried out in monkeys were usually done with single animals or small numbers of animals, and one could not be certain of occasional differences between acute and convalescent sera; (b) the viruses of recent human origin might have been of either low or high potency and virulence, and since the tests were carried out with unknown quantities of virus (in terms of paralytic or infective doses), the comparative studies were consequently neither
