As for testis parameters of rats treated with Habbatus sauda oil, findings in this research were in line with a report of increased number of spermatids in Nigella sativa-treated rats [34]. Since thymoquinone is the major constituent found in Nigella sativa, it was believed to have protective effects on testicular parameters [41]. In another study, the protective effects of thymoquinone on testicular parameters had been proven [42]. In addition, coadministration of cisplatin and Nigella sativa oil on rats for a period of 21 days showed an evident improvement in the structure of testes [43].