Claude Bernard's discovery of glycogen in the liver had a profound influence both on physiology and on pathology. Take first its influence on pathology. Diabetes was known to Celsus, Aretæus, and Galen; Willis, in 1674, and Morton, in 1675, noted the distinctive sweetness of the urine; and their successors proved the presence of sugar in it. Rollo, in 1787, observed that vegetable food was bad for diabetic patients, and introduced the strict use of a meat diet. But Galen had believed that diabetes was a disease of the kidneys, and most men still followed him: nor did Rollo greatly advance pathology by following not Galen, but Aretæus. Later, with the development of organic chemistry, came the work of Chevreuil (1815), Tiedemann and Gmelin (1823), and other illustrious chemists: and the pathology of diabetes grew more and more difficult:-- "These observations gave rise to two theories: the one, that sugar is formed with abnormal rapidity in the intestine, absorbed into the blood, and excreted in the urine; the other, that diabetes is due to imperfect destruction of the sugar, either in the intestine or in the blood. Some held that it underwent conversion into lactic acid as it was passing through the intestinal walls, while others believed it to be destroyed in the blood by means of the alkali therein contained."[3] [3] _Reynolds' System of Medicine_, vol. v., art. "Diabetes Mellitus." Thus, before Claude Bernard (1813-1878), the pathology of diabetes was almost worthless. And, in physiology, his work was hardly less important than the work of Harvey. A full account of it, in all its bearings, is given in Sir Michael Foster's _Life of Claude Bernard_ (Fisher Unwin, 1899). In Bernard's _Leçons sur le Diabète et la Glycogenèse Animale_ (Paris, 1877), there is a sentence that has been misquoted many times:-- _Sans doute, nos mains sont vides aujourd'hui, mais notre bouche peut être pleine de légitimes promesses pour l'avenir._ This sentence has been worked so hard that some of the words have got rubbed off it: and the statement generally made is of this kind:-- _Claude Bernard himself confessed that his hands were empty, but his mouth was full of promises._