se.” Pharmacological Activity Antiparasitie Activity A study on mice demonstrated that myrrh at an oral dose of 500 mg/g for five days before infection or one day after infection bad a valuable schistosomicidal effect against the different maturation stages of Schistosoma mansoni.^’ This is the organism that causes bilharzia. In addition, the livers of mice treated with myrrh (500 mg/g orally) for eight weeks after infection with schistosoma showed a marked reduction in degenerative changes.’^ Myrrh has also demonstrated activity against S. mansoni worms in wiYro.’•’Not all the studies have been positive. There is one reported study where myrrh failed to exhibit any significant antiparasitie activity in mice and bamsters infected with S. mansoni.^^ Molluscicidal Activity Snails act as vectors for S. mansoni, hence molluscicidal activity can play a role in the prevention of biiharzia (sehistosomiasis). The moUuseicidal properties of the oil extract of myrrh were tested against the Egyptian snail species Biomphalaria alexandrina, Bulinus truncates, and Limnaea cailUaudi. The impact of the extract on the egg clutches of B. alexandrina and L. cailliaudi was also evaluated. Snails and their eggs were exposed for 24 and 48 hours at 22°C to 26°C to various concentrations of the extract. The results showed different susceptibilities. B. alexandrina showed higher LD50 and LD90 (155,195 ppm) concentrations than B. truncatus (50,