THE publication by Sabin1 of the neutralizing antibody test for the diagnosis of toxoplasmosis encouraged us to utilize this laboratory method in cases of suspected toxoplasmic choroiditis. It was our early ambition to make clinical observations in a few cases, in which laboratory tests had proved that the lesions of choroiditis were undoubtedly positive or negative for Toxoplasma, and with this experience to be able to make a presumptive diagnosis of the disease, without necessity of finding a coexisting cerebral calcification or a positive reaction to the neutralizing antibody test to confirm the diagnosis. Such observations during the past three years prompt us to state that until a more accurate or a more convenient means is devised, the neutralizing antibody test must be used if a relatively certain diagnosis is to be made.
Callahan's2 estimate that the incidence of toxoplasmosis in the St. Louis population is about 2