The formation of the insignificant quantity of sugar in the body goes on of itself regularly, without it being possible to perceive any consequent striking alterations in the organism. The manner in which sugar is formed in the body under normal conditions has in recent years been thus explained. The sugar contained in the blood in healthy persons is reckoned as not higher than about 0.15 per cent. In those who suffer from diabetes it may rise to 0.44 per cent. If sugar is present in the blood, that it passes thence into the urine can be easily explained, seeing that the excreted products of decomposition from the blood pass into the urine. Thus the sugar results from a portion of the food which is transformed into sugar, and so passes into the portal vein. (Strümpell.) There exists also in the liver and muscles a non-nitrogenous substance, glycogen, which is detected also in other organs. This glycogen probably arises partly from the carbo-hydrates of the food, but certainly from the albuminous substances taken with the food, which, when broken up, separate into nitrogenous products and glycogen. When the glycogen is once formed, we may regard it as an intermediate substance which is changed into sugar, probably by a saccharine fermentation, and then can reach the blood. How glycogen is transformed into sugar within the organism is unknown. Normally occurring sugar results from glycogen. CHAPTER III When, years ago, my attention was first attracted by the idea that, for the solution of our problem, we ought to turn our attention to the sugar in normal urine, no very exact tests for sugar were possible. The reactions were not very sensitive, the fact being that the surest evidence of the presence of sugar was obtained not from the reduction processes but from the method used by Brücker for preparing a potassium compound of sugar. Every investigation which I undertook in his times for the confirmation of my theory was very arduous. The few cases which I at first had under observation presented formidable difficulties. The occasion of my first turning my attention to sugar in the urine was a case of a woman who had borne five children, and, after violent and continuous mental excitement, was suddenly seized with diabetes mellitus. I frequently examined her urine, and always found an abnormal amount of sugar. She had twice given birth to children whilst suffering from diabetes, and on each occasion the child was a female. This fact struck me, because previously, whilst she was strong and well, she had borne sons only. But, on the appearance of the disease mentioned, she had two daughters in succession, of whom the first one lived and the other was still-born.