_Symptoms of diabetes._--The symptoms of diabetes are due for the greater part to the accumulation in the blood and excretion in the urine of unused sugar. On leaving the body, sugar carries water with it. A diabetic patient may pass many quarts of urine daily. This is a phenomenon like the drying of meats or fish by salting them. Water is subtracted in such amounts that the body dries; even the skin becomes dry, and the tongue may cleave to the roof of the mouth. Furthermore, much otherwise available food energy is lost with sugar in the urine. As much as a pound of sugar may be passed in a day. Consequently, the tissues starve in the midst of plenty. The appetite, therefore, is sharpened, but the more the patient eats, the greater becomes the wastage of food energy, and the more severe the symptoms. _Acid poisoning._--This is not all or, by any means, the worst. It so happens that fat, which under suitable circumstances, is readily metabolized, fails to oxidize smoothly when less than a certain minimum of sugar is being used. The fats, it is said, burn in the fire of carbohydrates. If a perfectly normal person is deprived of carbohydrate and fed only fat and a little protein, certain products of incompleted combustion of fat will accumulate in the body. These substances are acetone, aceto-acetic acid, and the hydroxybutyric acid. Acetone is not very poisonous, nor is hydroxybutyric acid, but aceto-acetic acid behaves somewhat after the manner of the anesthetics like chloroform. If a person has diabetes of some severity, acetone bodies may arise even when carbohydrate is fed because only _burning_ sugar prevents their formation, and in severe diabetes the carbohydrates fail to burn. _Diabetic coma._--In diabetes, therefore, such amounts of aceto-acetic acid may be formed that the patient is actually anesthetized and falls into unconsciousness. This is diabetic coma, which in the past has been the chief cause of death in the diabetes of children and young persons. The proper use of insulin should prevent these deaths from coma. THE STORY OF INSULIN _Minkowski’s discovery._--The story of insulin began a generation ago with the discovery of German investigators, Minkowski and von Mehring. This was in 1889, and until then the relation of the pancreas to diabetes was scarcely suspected, and no one had an idea where to look for the means to check the disease. The pancreas is an organ about the size of one’s hand which pours digestive juices into the intestine.