The general organic and certain inorganic substances taken into the economy are capable of decomposition and are found in this state in the secretions. ,

The animal organism is rich in ferments which are capable of causing hydrolytic decomposition of various substances (i. e., their division with the addition of water); and there is no doubt that drugs, like many of the normal constituents of the body, may be subjected to such changes and the destruction of the medical properties of the drug, or the creation of new medicinal principles be thereby produced.*

*Prof. L. Hermann.

In the consumption of substances by oxidation, a distinction must be drawn between complete and incomplete oxidation. Complete oxidation of organic substance is always accompanied by the formation of carbonic anhydride and water, and under special circumstances, by the lib.ration of nitrogen, and the formation of sulphuric and phosphoric acids; the nitrogen appears never to be oxidized, or even to be completely isolated, but, on the contrary, remains associated with the other elements with which it was combined before the process of oxidation took place, and appears as ammoniacal compounds in the excretions.*

The incomplete oxidation of drugs will depend upon the detection of special oxidation products, such as aldehyde for alcohol, benzol, or phenol for acetic acid, etc. Among the normal products of incomplete oxidation, whose increase is to be looked for, oxalic acid deserves notice.*

There is a limitation to the consumption of medicine in the economy for any given time. Small doses may be totally changed or destroyed, but when given in excess, a limited amount will only be consumed, and the surplus disposed of by one of the emunctories. For example: Caffeine when taken in therapeutic doses, is entirely destroyed in the system and when given in toxic amount is partially destroyed and partially eliminated by the kidneys, † Glycerine is absorbed from the alimentary canal, and when freely administered is in part eliminated, and in part burnt up in the system.:]: Alcohol in small doses is entirely consumed, in toxic doses it is eliminated in the form of acetone or aldehyde. Chloride of sodium in small doses is retained, but when given in excess, is detected in the urinary secretion. The same may be said of sulphides of potassium and sodium. Cod-liver oil is assimilated in the system, but in large doses, like all other oils, will appear in the foeces. § Sugar taken as food and resulting from digestion of starch, is consumed in the, organism and is never discharged.|| Honey does not take exactly this course; it is mainly consumed, but it has a volatile property that is eliminated from the lungs. But it appears that antifebrine is not always governed by any posological law, as it was never found at all in the urine, consequently it undergoes entire decomposition; but of its peculiar manner of elimination as a toxic agent we will speak hereafter.