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 The heat which could be hereby generated is withdrawn from the organism, and must be procured by fresh nourishment, in order to replace that which has been lost by an imperfect assimilation of the food.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.
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.