The penetration of the cercariae of Schistosoma mansoni into the skin and lymphatics of the mouse

Abstract

A series of 24 photomicrographs is presented which illustrate the mode of penetration of the cercariae of Schistosoma mansoni into the skin and lymphatics of the experimentally infected white mouse. Penetration is effected by a combination of lytic and mechanical means with a maximum of lytic effect against those tissues which offer greatest resistance to mechanical penetration. The cercariae penetrate between the hair follicles but may be seen to enter the bases of the latter when they lie in the path of vertically migrating larvae. The tail may be carried down into the hypodermal tissues before detachment. The deep fascia sheathing the muscle of the body-wall resists vertical penetration by cercariae and causes the latter to turn to horizontal wandering in the hypodermal connective tissue. Upon reaching a lymphatic vessel the cercariae enter it and so gain entry to the venous circulatory system.