It is necessary for a clear understanding of the chemical changes which occur on treating morphine in various ways, and for comparing its physiological action with that of the bodies so formed, that we should summarise at some length the exact position of our present knowledge regarding its chemistry and pharmacology.

Morphine has the composition represented by the formula C17H19NO3. It is generally supposed to crystallise with one molecule of water, but there is reason to believe that the composition of the hydrated base is really 8 C17H19NO3, 9 H2O, the water being present in the proportion of 1⅛ molecule. Morphine is a monacid base, forming neutral and readily soluble salts with all the stronger acids. Like all alkaloids, it is built up on the ammonia (NH3) type, and is a tertiary amine, all the hydrogen atoms having been replaced by more or less complex radicals.