One of the most important conclusions arrived at by Pavy in his Physiology of the Carbohydrates, is that the intestinal epithelium acts as a barrier to the passage of carbohydrates into the circulation by converting them into fats (p. 248 et seq.).

Although the fact that the amount of sugar in the portal blood varies with the amount of carbohydrates taken would seem to indicate that the intestinal epithelium passes sugar on to the blood for the most part unchanged, the well-known observations on the conversion of carbohydrates to fats in the animal body suggest at least the possibility that such a change as that maintained by Pavy may take place.