Human toxoplasmosis, a protozoan infection, was first encountered in infants as a severe disseminated encephalomyelitis,1after which it was observed in older children as a milder form of encephalitis2and in adults as a generalized infection with pulmonary involvement.3The large reservoir of spontaneous toxoplasmic infection in rodents and in birds is the most likely source of the human infection ; however, no definite evidence of the mode of transmission from the lower animals to man is available. The prominence and the regular occurrence of lesions in the eyes were stressed in previous papers of this series and in related publications in which the infantile form of the disease was first described.4These lesions, together with the symptoms and signs of widespread involvement of the central nervous system, frequently including internal hydrocephalus, convulsions which appeared at birth or soon thereafter and cerebral calcification detected by roentgenographic methods,