A novel structure in the stomach and intestine of two species of Australian marsupial mice

A tubular or sac-like structure with a well defined lumen which occasionally contained parasites was found in the outer muscle wall of the small and large intestine in 32 out of 40 male and 35 of 40 female marsupial mice of the two species, Antechinus swainsonii and Antechinus stuartii (Macleay). A similar structure was also found in the muscle layers of the stomach in 5 marsupial mice of both species. The cellular matrix of the structure appeared to be composed of randomly organized macrophage-like cells and in one case there was evidence of an inflammatory reaction to parasites within the lumen. The origin of this tube is either vestigial or the result of reactive changes.