The three groups are grape-sugar, cane sugar, and cellulose. In the urine grape-sugar occurs normally among the products of excretion in inconsiderable quantities. Under exceptional circumstances, in cases of polyuria, inosite can occur. (H. Voll, Neumeister.) In addition we find also a carbo-hydrate mentioned by E. Luther that would be of the character of dextrine, and probably owes its existence to the secretive activity of the urinary bladder. Upon boiling the urine with mineral acids we obtain substances which separate as brown flakes. We denote these “humin-substances” (_Huminsubstanzen_, Udránsky, Salkowski). In addition to these must be enumerated animal gum, isomaltose, pentaglycoses, lævo-rotary sugar, the conjugate glycuronic acids, etc. In conclusion, the occurrence of milk-sugar must be mentioned, which appears in the last days of pregnancy. The last-mentioned substances occur in very insignificant quantities, and are not to be enumerated among the ordinary constituent parts of the urine. * * * * * The carbo-hydrates may be, in many respects, of high interest for the activity of the organism in its metabolism, as they are found amongst the products of excretion only as final products of the completed transformation and using-up of the food. The excretion of a carbo-hydrate in the urine can be interpreted to mean that the process of combustion in the organism in question has not been complete. By some agencies, at present unknown to us, the efficiency of the organism becomes impaired in such a way that it does not fully use up all combustible substances. A number of substances can be excreted from the body which are capable of a further process of oxidation--for example, until they are oxidized into carbonic acid and water. The heat which could be hereby generated is withdrawn from the organism, and must be procured by fresh nourishment, in order to replace that which has been lost by an imperfect assimilation of the food. One substance which occurs in the urine, about which much has been written by various authors, by physiologists, by medical men, and by chemists, is of high importance for our inquiry. That is the _sugar found in normal urine_. * * * * * When this substance occurs in the human organism, no matter in how small a quantity, its presence always suggests the assumption that it ought not to have been secreted in the form of grape-sugar. For, if the organism possessed its full efficiency to deal with the necessary quantity of food taken, then one might also suppose that a substance such as grape-sugar, be the quantity never so small, would not be secreted in an unaltered form, but must be further used up, seeing that the sugar would be decomposed, oxidized, in short, burnt up.