The caecum of monotremes and marsupials
- 1A description is given of the caecal region of the gut in a number of monotremes and marsupials, covering most genera, some of which are now very rare and possibly even extinct. As in a previous memoir, particular attention is given to the peritoneal folds attached to the viscus and to its blood supply.
- 2Monotremes exhibit a simple caecum tethered by a single median fold, or none (e.g. Zaglossus).
- 3Marsupials as a group show a more complex arrangement, although, as in Primates, the caecum is typically anchored by a median anangious fold with flanking vascular folds on the morphologically sinistral and dextral sides. However, many complex specializations exist to modify this arrangement. One artery is typically the larger, and this is more often the sinistral than the dextral.
- 4The size of the caecum may possibly depend on some factor in the diet of the animal, but this cannot be simply the proportion of vegetable material it contains, nor is it the only factor concerned.
- 5Specialization within the viscus occurs in many marsupials, but never proceeds so far as to form an appendix caecalis.