The imperfect performance of an operation of this kind by the organism is not to be taken for a symptom of pathological processes. In point of fact, it has been impossible to recognize, in the case of individuals afflicted with this imperfection, any symptoms of processes of such a character as would furnish the remotest occasion for the appearance of disease. * * * * * When small quantities of saccharine matter are excreted, derived from carbo-hydrates which have been swallowed, or, on the other hand, formed within the human body, say from albuminous principles, it might be expected that this excretion, occurring repeatedly in different individuals, ought to be regarded as a normal metabolic process. Such an occurrence must be interpreted, in fact, in much the same way as other small anomalies which affect the organism, whose presence leads to no further consequences. But our attention must be directed, not to the sugar alone, but to a number of other so-called reducing substances, because these, as regards certain reactions, resemble grape-sugar, and have to be distinguished from it. * * * * * In the year 1858 my highly-revered master, E. Brücke, drew attention to the presence of grape-sugar in normal urine. The foundation of the theory of normal glycosuria was laid by his obtaining the potassium compound of sugar (_zuckerkali_) from large quantities of urine. His theory has been since much elaborated, and a great deal written both for and against it. When this symptom in the urine reaches a certain proportion per cent., the condition of the individual must be described as diseased. If we apply qualitative chemical tests for sugar, we soon find that they are disturbed by a number of reducing substances which exist in the urine, and it is often difficult to determine whether the processes used to discover the sugar do not produce more reducing substances than the sugar itself. Bence-Jones agrees with Brücke’s opinion respecting the presence of sugar in normal urine, and insists upon its power to rotate the plane of polarization to the right. More recent authors, Ivanof, Huizinga, Pavy, Abeles, have stated this fact in different ways, and it yet remains to be verified. The fact existed, but not without meeting with contradiction. Maly, Seegen, Friedländer, and many others sought to oppose the view. Although in many cases with the commonly used reactions it is impossible to demonstrate the presence of sugar in samples of urine, nevertheless, the sugar has been isolated in considerable quantities, by means of precipitation with acetate of lead and ammonia, and by subsequent decomposition of the precipitate with sulphuretted hydrogen (E. Ludwig), after which it has been successfully tested and recognized by characteristic reactions. * * * * *