Measurements of the oxygen tension in the lumen of the small intestine of the domestic duck.

The aim of the work described in this paper was to measure the oxygen tension across the lumen of the small intestines of domestic ducks, with special reference to the region of the lumen near the villi. These data are required to enable the metabolism of the acanthocephalan parasite, Polymorphus minutus, to be studied in vitro. Many parasites of vertebrates live in this region of the lumen, for which Read (1950) proposed the name paramucosal lumen in order to emphasize that its physico-chemical properties are different from those of the rest of the lumen. Adults of P. minutus are found in the intestinal wall and paramucosal lumen of many birds including domestic ducks. The majority of the worms live in a zone consisting of about 20 % of the length of the intestine, situated posterior to the yolk stalk (Crompton & Harrison, 1965). They become attached to their hosts by means of a spiny proboscis which bores as far as the longitudinal muscle layer of the gut wall. The host reacts against the proboscis by surrounding it with fibrous material, but the neck and spiny anterior portion of the trunk of the worm do not appear to stimulate a host reaction although they also are in contact with the tissues of the gut wall. The oxygen tension of venous blood of domestic ducks is about 35-40 mm. Hg (Sturkie, 1954). Thus, it may be postulated that a tension near this value exists in the crypts of Lieberkiihn, through which the parasite burrows. The remainder of the trunk of the parasite, which in nature is flattened dorso-ventrally and is about 1-5 mm. thick, lies in contact with the villi on one side and with the contents of the gut lumen on the other. The method described here was devised to investigate the region where the trunk of the worm is found.