Summary

This 1922 paper by Frederick Banting and Charles Best reports the discovery that an extract from the pancreatic islets of Langerhans (insulin) can reverse the symptoms of diabetes mellitus in dogs. The central thesis is that the internal secretion of the pancreas, produced by the islet cells, is a substance that regulates blood sugar, and its deficiency causes diabetes. The authors describe their method of ligating the pancreatic duct to cause degeneration of the acinar tissue, leaving the islets intact, then extracting the active principle. They demonstrate that injecting this extract into diabetic dogs lowers blood glucose and glycosuria, and prolongs survival. The paper provides the first concrete evidence that a pancreatic hormone can treat diabetes, laying the foundation for insulin therapy. A reader takes away the experimental proof that diabetes is a hormonal deficiency disease, and the specific surgical and extraction techniques that enabled the isolation of insulin.

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Key concepts

Islets of Langerhans — The clusters of endocrine cells in the pancreas that produce insulin, distinct from the exocrine acinar tissue.
Pancreatic duct ligation — A surgical technique used to destroy the exocrine pancreas while preserving the islets for hormone extraction.
Blood glucose reduction — The key physiological effect of the pancreatic extract, measured in diabetic dogs to confirm its therapeutic action.
Glycosuria — The presence of glucose in urine, used as a marker of diabetes severity and reversed by the extract.
Internal secretion — The concept that the pancreas releases a hormone into the bloodstream, as opposed to external secretion via the duct.