Excepting in a purely vegetarian diet which requires the administration of a variable quantity of chloride of sodium, there is no necessity for making any special provision for the addition of mineral substances to the menu, as they are so closely associated with the food-stuff's that more than enough is usually obtained with an ordinary mixed diet. During the process of digestion they are, in the first instance at all events, to a great extent separated from the alimentary principles, and then pass through the intestinal capillaries to the liver and the systemic circulation, although a certain proportion, e.g., iron and iodide of potassium, may reach the blood by way of the thoracic duct. On account of the difficulties attending the investigation, it can hardly be wondered that so little is known about the subject, or the ultimate disposition either of water or the soluble salts. We are well aware that the absorption of the one is closely bound up with the absorption of the other, because the result of prolonged research has proved that common salt and the other soluble inorganic salts constitute the osmotic factors in absorption and excretion.

Salt solution (NaCl) unquestionably passes from the bowel into the blood-vessels and lymphatics of the intestinal walls, but just how far the cells themselves as living units are engaged or involved in this process it is impossible to say. A saline solution cannot pass into the capillaries of the bowel by osmosis without displacing something from the bloodvessels. It is quite possible this is one of the factors contributing to the production of the faeces, because it is now well-established that a considerable proportion of the contents of the residue known as "faeces" has been eliminated by the bowel wall. Far too little is known, however, on the subject, and what part is played by diffusion, filtration, and imbibition in addition to osmosis.