_Insulin a welcome discovery._--The discovery of a method for obtaining insulin in a form suitable for use in treating diabetes is a cause for genuine rejoicing. The sensational newspaper and magazine articles that greeted the discovery were, in a sense, a public expression of such rejoicing, and their exaggerations may be forgiven if this is remembered. The effort to gain an understanding and a sure method of controlling diabetes has taken years, and while the scientist delved in his laboratory, the seemingly unconquerable disease continued to take an ever-increasing toll of young and aged victims. In New York City, for instance, where statistics collected by Dr. Emerson are most reliable, the deaths from diabetes in 1866 were only 1 for each 2,437 deaths from all causes. In 1923, one death in every fifty-one was due to diabetes. The diabetic death rate in New York City was trebled between 1880 and 1920 for ages up to forty-five years. For ages of forty-five and more, it was quintupled. There are probably more than a million patients with diabetes in the United States. No wonder then that mankind in general was overjoyed when the news came that the young Canadians, Banting and Best, had discovered insulin. THE NATURE OF DIABETES _Diabetes a disorder of metabolism._--What is this insulin and what does it do? Before this is answered, the nature of the chemical disorder that is called diabetes must be somewhat understood, and to supply this understanding, a partial review of the chemistry and physiology of nutrition must be made. The processes of life are largely chemical. The warmth of the body is provided by combustion, oxidation of food. If the supply of food is discontinued, life ends, and the body cools exactly as a gasoline motor stops and cools off when its supply of fuel is exhausted. Similarly, if the machinery for transforming food into energy is impaired, life will lag. This is what happens in diabetes; the disorder is much like that of a motor which misses fire when its ignition system is out of order. Food, like gasoline, contains energy, and life results from the conversion of this potential energy into body heat and muscular activity. The processes involved in this conversion are spoken of collectively as “metabolism.” Diabetes is a disorder of metabolism. There are other disorders of metabolism, but none so common as that of diabetes.