There is some difficulty in following droplets of fat across the space which intervenes between the epithelium of a villus and its lacteal radicle. It has been asserted that leucocytes act as carriers, catching the droplets as they are extruded by the epithelial cells, and bearing them into the radicle, where they set them free. Undoubtedly, many leucocytes are present in the lymph-spaces of a villus. After a meal they are found charged with fat. But it is hardly in accord with what we know of the character of a leucocyte to suppose that it will let go fat which it has once ingested into its own body-substance. A leucocyte is not a disinterested organism. If fat droplets are floating across from the epithelium to the lacteal, leucocytes are pretty certain to steal some of them. But we know of no other case in which they give up what they have stolen, unless it be something which is injurious to their own health. Even then they usually cling to it, whether it be a germ or a particle of soot, until their own dissolution sets it free. Neither proteins nor sugar reach the lacteal radicle. Both these substance are absorbed from the lymph in the tissue-spaces of the villus by the blood-capillaries and venules which traverse them. The veins of the intestine unite to form the portal vein, up which proteins and sugar are carried to the liver, where they are stored, to be doled out into the blood-stream as the tissues need them. =Bacteria of the Alimentary Canal.=—The enzymes (ferments) of the several digestive juices are not the only agents which modify the constitution of the foods within the alimentary canal. Throughout the whole of the tract conditions are in many respects favourable for the growth of putrefactive organisms. Mouth, stomach, small and large intestine, has each its special bacterial flora. It is doubtful whether any of these organisms, with the single exception of the bacteria which in herbivorous animals break up cellulose, are favourable to digestion. That they are not necessary has been shown by an ingenious experiment on new-born animals. Guinea-pigs born in an aseptic chamber, through which filtered air was drawn, and fed every hour on sterilized milk, throve and put on weight. When killed at the end of eight days, no germs were present in their alimentary tracts. Yet in all animals under ordinary conditions bacteria are present in great numbers, at any rate, after the nursing period, and, for good or ill, produce important fermentations. Only a single bacillus (_B. bifidus_), and that a friendly germ, is, it is asserted, present in the intestines of an infant at the breast; whereas a bottle-fed baby houses a variety of parasites.