as we can judge, the contents of the small intestine are alkaline. Conditions are therefore favourable for the formation of soap. But in carnivora the contents are acid throughout the greater part of the canal. Acid, it need hardly be stated, prevents saponification. Yet carnivorous animals have an immense capacity for absorbing fat. Fatty acids are soluble to a moderate extent in bile. It is possible that, fats having been split into fatty acids and glycerin, the fatty acids are carried into the cells in solution in bile. But if in carnivora bile actively participates in the absorption of fat, there is no reason opposed to its having the same function in Man; and, indeed, all observations which have been made upon patients in whom the bile was, for some reason, diverted from the intestine, and in animals in which a fistula of the gall-bladder has been artificially produced, show that in the absence of bile the absorption of fat is considerably decreased. Yet there is no reason for thinking that bile is secreted for the purpose of facilitating the absorption of fat. Just as much bile is poured into the intestine of a cow which is feeding upon grass as into the intestine of a pig or a dog when the animal is consuming a very large quantity of fat. Nevertheless, it appears to be certain that, not in carnivorous animals only, but also in herbivorous animals, the assistance of bile is necessary for the satisfactory absorption of fat. Doubtless the co-operation of bile and pancreatic juice is more important to carnivora than it is to herbivorous animals, in which, owing to the alkalinity of the contents of the intestine, all fatty acids liberated by the action of pancreatic juice might be converted into soluble soaps. The problem of the form in which foods enter the absorbing cells is intimately associated with the further problem of the form in which they leave them. In the villus, and even within the epithelial cells, fat appears abundantly as such. If, as we have reason for believing to be the case, it enters in the form of soap and glycerin, the re-formation of fat is an illustration of the synthetic power of the tissues. For the purposes of the economy it is needed as fat, and not as the constituents of fat. There is no reason for thinking that at any stage in its future progress it is again split into fatty acid and glycerin. We cannot see absorbed proteins with the microscope, as we can see fat, nor can we apply chemical tests which will distinguish between the proteins which the cells contained before digestion commenced, and the proteins which they have received as its result. Nevertheless, it is certain that peptones are reconverted into proteins as soon as they are absorbed. They are not to be found in blood or lymph. If the peptones absorbed after a proteid meal remained as such after they passed through the wall of the alimentary canal, they would produce various undesirable results.