The digestive tracts of herbivora appear to be of two main types. Firstly that of the ruminant, in which fermentation with production of fatty acids takes place in the rumen prior to the foodstuffs entering the true stomach and small intestine so that by the time the food passes into the large intestine all significant absorption has been completed. The main function of the large intestine in this case appears to be abstraction of water. Secondly, those of the group represented by horse, guinea-pig, rabbit and others which, although living and thriving on the same diet as ruminants, have no rumen but possess a large caecum in which, it is presumed, fermentation proceeds in much the same manner as in the rumen. In this case it seems logical to expect provision for absorption from either the caecum or colon or both. For investigating the functions of the caecum and colon one of this group of animals, the guinea-pig, has been selected because it is easy to work with and readily procurable.As it has been shown that monosaccharides are not absorbed from the large intestine of either the carnivorous dog (McNealy and Williams, 1929) or the omnivorous rat (Davidson and Garry, 1939), the first group of experiments in this investigation was devoted to studying the absorption of monosaccharides from the large intestine of the guinea-pig.The investigation involved the introduction of glucose, fructose, galactose and xylose into isolated intestinal segments of the guinea-pig with their subsequent recovery and estimation; and the determination of blood glucose levels before and after introducing glucose into segments of the gastrointestinal tract.
METHOD.Sodium pentobarbital anaesthesia was administered intraperitoneally. The segment of intestine being studied was cut at either end, washed tlirough with physiological saline until the washings were quite clear, then firmly ligated at both ends. The isotonic solution of monosaccharide was introduced from a burette directly through a fine hypodermic needle inserted through the wall of the gut until the segment was just filled without overdistention. After 2 to 2^ hours the intestinal segments were removed, opened and I This work was done with the aid of a grant from the Commonwealth Research Fund for Universities.