*Assimilation.*—Digestion, absorption, circulation, and storage of foods are the processes that finally make them available to the cells in the different parts of the body. There still remains another process for these materials to undergo before they serve their final purposes. This last process, known as _assimilation_, is the appropriation of the food material by the cell protoplasm. In a sense the storage of fat by connective tissue cells and of glycogen by the liver cells is assimilation. The term is limited, however, to the disposition of material with reference to its final use. Whether all the materials used by the cells actually become a part of the protoplasm is not known. It is known, however, that the cells are the places where most of the oxidations of the body occur and that materials taking part in these oxidations must, at least, come in close contact with the protoplasm. Assimilation, then, is the last event in a series of processes by which oxygen, food materials, and cell protoplasm are brought into close and _active_ relations. The steps leading up to assimilation are shown in Table II. TABLE II. THE PASSAGE OF MATERIALS TO THE CELLS MATERIALS DIGESTION ABSORPTION ROUTE TO STORAGE CONDITION THE GENERAL IN THE CIRCULATION BLOOD Proteids Changed In passing Through the Become a As proteids into into the portal vein part of the in proteoses capillaries, to the protoplasm colloidal and the liver and of all the solution. peptones by proteoses from there cells. the action and through the of the peptones hepatic gastric and change into veins into pancreatic the the juices. proteids of inferior the blood. vena cava. Fat Changed In passing Through the As fat in Chiefly as into fatty into the lacteals to the cells minute oil acid, lacteals, the of droplets. glycerine, the thoracic collective and glycerine duct, by tissue. soluable unites with which it is soap by the the soluable emptied bile and soap and into the pancreatic fatty acid left juice. to form the subclavian oil droplets vein. of the blood. Starch Reduced to Enters the Through the As glycogen As dextrose