Heat-Labile Serum Systems in Fresh-Water Fish

Abstract
Serum specimens from 18 specimens of 12 different species of freshwater fish were examined for their ability to kill Toxoplasma nonspecifically. This ability was present in all sera except those of two of three great northern pike. The effect was destroyed by exposure to 53°C, 56°C, or zymosan. Complement was demonstrated in all sera except that from one great northern pike, when rabbit erythrocytes were used in the indicator system.