Attachment of the Sheep Hookworm to the Common Sheep Tapeworm

THE study of the manner of feeding of the nema-todes inhabiting the alimentary canal of vertebrates is one of the comparatively recent developments of helminthology. Hoeppli, Wetzel and others have shown that many nematodes which possess a well-developed buccal capsule-typified in the Strongylidse and the Ancylostomidæ-are probably tissue feeders. Thus Wetzel1 describes the feeding habits of Chabertia ovina (Gmelin, 1790) from the large intestine of the sheep and says: " Longitudinal sections of specimens attached to the mucosa show that the worms have drawn a portion of the stratum glandulare into the sub-globular toothless buccal capsule. On its base the tissue is strongly pressed together by the mouth wall and the anterior margin of the buccal capsule, forming a neck-like constriction. Opposite the place to which the parasite is attached a flexure is to be seen in the muscularis mucosa and in the sub-mucosa As to the marked regressive changes of the swallowed tissue and the necrotic masses at the bottom of the buccal capsule we have to assume further a histolytic action of the parasite From a general physiological point of view the whole process is nothing other than a pre-digestion of the elements of the propria mucosa before they are swallowed by the worm."