Abstract
Summary: Groups of mice were infected with 1,5 or 10 cysticercoids of Hymenolepis microstoma. Infections were terminated with the anthelmintic ‘Zanil’ after 5, 15 or 30 days and the mice challenged with 6 cysticercoids. The growth of the worms in the secondary infections decreased as either the intensity (number of cysticercoids administered) or duration of the primary infections increased. It is postulated that the results have an immunological basis.