On the Early Stages of Fasciola hepatica Penetrating into the Liver of an Experimental Host, the Mouse: a Histological Picture

Abstract

1. Excystment of the metacercariae of Fasciola hepatica by perforation of the inner cyst was witnessed, but the factors which control activation of the larva remain undetermined.2. Excystment occurred in two instances when cysts were administered to mice by intra-peritoneal injections, active young flukes being recovered.3. Excystment occurred when cysts were administered to one week old chicks and free flukes were recovered from the abdominal cavity in three instances, but liver lesions were not observed.4. By means of photomicrographs an attempt has been made to demonstrate that young flukes feed primarily on hepatic cells and that they show a preference for this diet. Blood is inevitably included in the diet of young flukes, but it is claimed that these are not truly blood feeders.5. Young flukes recovered from the liver of the mouse range in length from about 0·3 mm. at 3–4 days to 4·85 mm. at 28 days from the time cysts were administered (per os). This accords fairly well with data obtained by Sinitsin and by Schumacher in respect of flukes from rabbits and guineapigs respectively.