When starch is boiled with diluted nitric, sulphuric or muriatic acid for thirty-six to forty hours, it becomes colorless and thin like water, and is converted into a species of sugar. A similar process takes place when starch is taken as food, the diastase of the saliva, and the pancreatic and intestinal juices change starch into _glucose_, in which form it is ready for nutrition. Cane and other sugars introduced into the system as ingredients of fruits and vegetables are not absorbed as such, but undergo a process of digestion which converts them into grape sugar or glucose; after that they are suitable for nutrition and absorption into the blood, but not before. The digestion of starches and sugars has been incidentally referred to as not taking place in the stomach but in the upper portion of the small intestine, through the agency of the pancreatic juice which has the peculiar property of converting farinaceous and saccharine matters into grape sugar. But this transformation into grape sugar is not the final product of digestion. In the normal process of intestinal absorption the grape sugar is taken up by the portal capillary vessels and carried to the liver, where under the influence of this organ it is changed into liver sugar or glycogen, and it is as glycogen that it again enters the circulation, to disappear in the lungs. But if the liver from disease or other causes fails to perform this task, the glucose passes through the organ unaltered, and as such again enters the circulation where it acts as an irritant and finally is eliminated by the kidneys in the urine giving rise to the affection known as diabetes.