Abstract
Mice given food containing fenbendazole to prevent a reinfection with Syphacia muris were treated with inducers of the hepatic microsomal monooxygenase system. Specific induction values and factors were the same as found previously in similar mice infected with Syphacia muris. There was a decrease in the total hepatic monooxygenase system by 20-40%, associated with a similar decrease in the total microsomal protein. As this was found in both experimental and control mice, the induction factors of the total values remained also unaltered. Thus infection by Syphacia muris not only retarded the growth of young mice but also accelerated the development of their hepatic monooxygenase system.