In a previous article1 it was reported that the amount of water that it was possible to cause a dog to excrete by the intravenous injection of glucose was directly proportional to the alkalinity of the blood as measured by the carbon dioxide combining power of the plasma (Van Slyke). The level of carbon dioxide of 45 is the critical point and if the dog is below that level of alkalinity, dehydration by glucose injection is impossible, all the water being "fixed" by the colloids or at least being in a relatively firm combination with the colloids. Above that level, an increasingly large amount is held in a freer or looser combination, "free" water acts as a body reserve. A continuation of these studies, using hypertonic salt solution as the dehydrating agent, has yielded similar results. Dogs were injected intravenously with a 5 per cent solution of sodium chloride at