Juvenile Stages of Fasciola hepatica in the Liver of the Mouse

Abstract

MOST biologists agree that in the latar stages of its life-cycle Fasciola hepatica wanders through the liver towards the bile ducts, where maturity is attained. When cysts containing metacercariæ are ingested along with herbage to which they are attached, the larvae are activated in the intestines of the host and are then able to emerge from the cysts, each of which develops a minute perforation. The young flukes then penetrate the wall of the intestines, creep about over the abdominal viscera and eventually enter the liver. Much research and some controversy were necessary before this migration became established beyond any doubt. Schumacher¹ has reviewed the literature bearing on this problem, and himself carried out experiments of a classical nature, which produced much valuable information concerning the time relations of the various stages of the migration in guinea pigs. He also gave an account² of the histological appearance of young flukes in the liver of the host 64 hr. after cysts were fed, but this is a very incomplete study and practically no other information of the same kind is available in the literature of fascioliasis. I have studied the early stages of migration through the liver of the definitive host, the mouse having been chosen to minimize the rather laborious task of serializing sections of infected liver.