The Occurrence of Lactase in the Alimentary Tract of the Chicken

In the experiments reported in the preceding paper (p. 597) it was found that lactose, fed to hens, does not appear in the excreta in appreciable quantities until excessive amounts are administered—a finding thoroughly in agreement with our present knowledge of sugar-feeding in human beings. Since lactose is assimilated from the alimentary canal of chickens, and since assimilation of disaccharids is normally preceded by hydrolysis into monosaccharids, lactase would be expected to be present in some part of the alimentary tract. However, the possibility of bacterial fermentation accounting for the disappearance of lactose must be considered. Previous investigations are not entirely in agreement in regard to the presence of lactase in the alimentary tract of the fowl. Portier (4) in 1898, using the osazone method for the detection of monosaccharids formed by the action of the enzym extracts on a lactose solution, found no indication of lactase in the intestines of birds. This was confirmed a year later by the extensive investigations made by Weinland (6) who, using the polarimetric method, found no indication of lactase in the intestines of fowls. He states, however, that the enzym is produced in the intestines of fowls if they are fed on milk and lactose. Bieri and Portier (J), using the duck in their experiments, found in one case, on feeding lactose and milk, that the intestines produced lactase, but a second experiment failed to confirm the first. Plimmer {2), in an extensive investigation on the subject of adaptation of the intestines to lactose, found that the intestines of fowls are naturally free of lactase and, furthermore, that lactase was not produced when lactose and milk were fed for long periods of time. Plimmer used Allihn's reduction method for the estimation of the degree of hydrolysis of a lactose solution produced by the enzym extracts. In a recent study on the distribution of enzyms in the alimentary canal of the chicken, however, Plimmer and Rosedale (3) found lactase to be present in the crop, but absent in the proventriculus and intestines. The presence of the enzym was determined by incubating at 37 C. a 4 per cent lactose solution with portions of boiled and unboiled extracts of the various organs for two days or more, removing the proteins, and determining the reducing sugars by reduction of Fehling's solution. The observed difference in reading between the boiled and unboiled solutions indicated whether or not hydrolysis by lactase had occurred. In the present investigation a similar study has been made. This inquiry did not extend, however, to the detection of lactase in the