Literature relevant to the function of avian caeca was reviewed. The alimentary tract of birds and differences between it and the mammalian tract, including rates of food passage were considered. Observations on caecal form and presumed function from the early nineteenth century onwards were presented. Work on caecal anatomy and vascularization was outlined. Caecal flora and the effects of antibiotic feed and of caecectomy were considered. A range of suggested caecal functions and absence of function were discussed. Caeca of a relatively homogeneous sample of chickens were studied to provide a concept of intra-specific variation and a basis for comparison. Variation in intestines and colorecta were measured. Sizes and structures of caeca and caecal linings were studied and illustrated. Experiments were made on the folds of Kerkring and their possible role in caecal distension. Linings of chicken "ileum" and colorectum were described and illustrated for purposes of comparison. Statistics of caeca of flamingoes, wildfowl, moorhens and coots were recorded and standard deviations and coefficients of variation of caecal lengths and body weights determined. The ratios of mean caecal length to mean body weight for each species were calculated and expressed graphically. Intra-specific distributions of caecal lengths for European Whitefront geese, Barnacle geese, Mallards and European wigeon and body weights for the first three species were shown. Differences between healthy and diseased birds were shown and discussed. The hind guts of nine tribes of waterfowl, of Red grouse, Black-headed gull and Tinamou were dissected. Drawings of their caeca, caecal mouth sections, caecal linings and colorectal linings were made and linings photographed. A selection of these was presented. Particle analysis of hind gut ingesta was made on four birds. Caecal and colorectal lengths in wildfowl were compared. The functional implications of gross caecal structure were discussed.
|Date of Award||1978|