The effects of various digestive enzymes, fresh biles, and bile acids on the hatching and activation of the eggs of Taenia saginata, T. pisiformis, T. solium, Hymenolepis nana, and Moniezia expansa have been investigated. On the basis of the results of the present study author attempted to elucidate the specificity of host-parasite relationships in the tapeworm infections. The results were summarized as follows: In case of the ova of T. saginata, pretreatment with artificial gastric juice before contact of intestinal juice is required to bring the disintegration of the embryophore and activation of the embryo. However the ova of T. solium and T. pisiformis may be disintegrated and activated directly into the artificial intestinal juice without the above pretreatment. Among the digestive enzymes applied in this experiment, trypsin was found most effective on the hatching. No hatching of the ova of H. nana and M. expansa was observed in the above artificial hatching-activating solutions. The fresh biles and bile salts were more effective on the hatching and activation of Taeniid ova than sodium taurocholate and sodium deoxycholate. It is turned out that the digestive enzymes or bile acids in the intermediate hosts may, not apparently be essential factor of determining the specificity of host-parasite relationships.
