Paul Langerhans, 1847-1888.

Time and history weave patterns with seemingly unrelated facts, as the weaver of a Persian rug blends varied threads through his loom to produce a design of ageless beauty. So it is with the facts of medical knowledge. Gathered and contributed by many workers, they may seem inconclusive or even insignificant at the time of their publication. But when they have been properly assembled and wisely interpreted, they, too, make patterns — of knowledge, if not of beauty. Such are the materials of scientific achievement in medical history. Today, every medical student the world over knows of the islets of Langerhans. Their textbooks tell them that the islets of Langerhans are cellular structures within the pancreas, and that these structures have an important relationship to diabetes. But very few know anything about Paul Langerhans; who he was, when and where he lived, and how he made his discoveries. The name of Langerhans has already endured in medicine for 85 years, and it will undoubtedly be preserved in medical annals for centuries to come. The most complete source of biographical information on Paul Langerhans is an essay by Morrison, whose interest in Langerhans was motivated by a search for outstanding contribution to medicine made by men still in their undergraduate years. This was an interesting approach to the biography of a man, and it should be of particular interest to members of the American Diabetes Association. Paul Langerhans, working in Virchow's laboratory at the Berlin Pathological Institute, began the study of anatomy of the pancreas in 1867 and reported his findings in 1869. A similar instance of medical discovery by an undergraduate student of medicine occurred on this continent within our own lifetime. At the University of Toronto, a graduate student in physiology while still an undergraduate student of medicine, working with Dr. Frederick Banting in 1921-1922 became the co-discoverer of insulin. His name is Charles Best. Never underestimate the powers of a medical student! That is something for oldsters to keep in mind, as we tread the corridors of our schools of medicine. Paul Langerhans was born in Berlin on July 25, 1847. His father, Dr. Paul Langerhans, was a physician; his mother (nee Keibel) was a cousin of Franz Keibel, the eminent histologist. One brother, Robert Langerhans, an assistant to Virchow, was professor of pathology and another brother, Richard Langerhans, was an honored practitioner of medicine in Berlin. As a student in Jena, Paul was the pupil of Ernst Haeckel, his "adored teacher." Later in Berlin, Paul was influenced particularly by Julius Cohnheim and Rudolf Virchow, with both of whom he had developed close friendships. In all of this we see what can happen when good seed is planted in good soil, and when a good inheritance finds a good environment. In the time of Langerhans, Claude Bernard had already demonstrated that the pancreas played an important role in the digestion and assimilation of carbohydrate, protein and fat. At that time the pancreas was simply described as a racemose gland, containing a mass of infiltrating fat. The adjective racemose was applied in a purely morphologic sense, intended to convey the picture of a raceme plant in which the flowers are attached to short stalks which spring from the main stem, like the flowers of the lily-of-the-valley. This description is quite applicable to the appearance of the glands of external secretion of the pancreas, but unfortunately it revealed little more than that. Of the existing knowledge pertaining to physiology of the pancreas at that time, Langerhans said, "There is indeed hardly another organ in which there is such glaring contrast between the brilliant results of physiologic research and the complete darkness in the realm of anatomic knowledge. Practically all that receives any thorough consideration from the anatomic point of view is the relationship of this gland to the peritoneum or whether the opening of this or that excretory duct is at a higher or lower level." Langerhans' early observations were made on the rabbit; later he studied the salamander, guinea pig, dog, cat, pigeon, snake, frog, hen, as well as man. He studied the