Previous investigationA previous investigation into the mortality of diabetics was made by A. J. Steeds following the analysis of data based upon a large London clinic. The present paper is based on data derived more recently from the experience of the patients attending a large Birmingham clinic.Diabetes mellitus2. Diabetes mellitus is a very ancient disease which may be described as a disturbance of the normal insulin mechanism of the body. The pancreas is a gland which secretes insulin for the purpose of converting sugar and starches into the energy forms required by the body (the metabolism of carbohydrates) and disturbance in this metabolism is accompanied by an abnormality in the breakdown of fats. Apart from physical damage to the pancreas the causes of diabetes are various and obscure (although they are thought to include heredity, overweight and, in females, a high level of childbearing). It is generally accepted that diabetes in young lives is a more severe form associated with insulin deficiency, whereas in older lives the disease is of a milder type, but there are many exceptions to this broad division.