A lokacin, babu wanda, har ma da d'Hérelle, ya san ainihin abin da phage yake. D'Hérelle ya yi iƙirarin cewa kwayoyin halitta ne da ke haifuwa, ta wata hanya suna ciyar da ƙwayoyin cuta. Wasu, Nobelist Jules Bordet shugaba a cikinsu, sun yi tunanin cewa phages sun kasance sunadarai marasa rai, musamman enzymes, waɗanda suka riga sun kasance a cikin ƙwayoyin cuta, kuma kawai suna haifar da sakin sunadarai masu kama da juna, suna kashe ƙwayoyin cuta a cikin tsari. Saboda wannan rashin tabbas, da d'Herelle ta amfani da phages ba tare da wata shakka a kan mutane ba, aikinsa yana ƙarƙashin harin ci gaba daga sauran masana kimiyya. Ba sai an lura da phage na farko a ƙarƙashin na'urar lantarki ta Helmut Ruska a 1939 ba ne aka tabbatar da gaskiyarta. Tambaya ɗaya ita ce: Menene D'Herelle bai ɗauka da gaske ba daga abokan aikinsa?
yin amfani da phages ba tare da yin shakka ba a kan mutane