laborious construction on the part of the manufacturer, operating under chemical laws. Gradually there has arisen a new branch of the science, whose aim is to produce artificially new compounds out of old material; and, since the living vegetable and animal offer familiar though mysterious examples of the same process, it is only natural that the philosopher should have tried to obtain, by known methods, some of those results which are so silently and wonderfully wrought out by the substance of living tissue. It will be the object of this paper to indicate, in a non-technical way, some of the steps which have been taken in the effort to compete with vitality.
The word synthesis, in its broad or general acceptance, signifies the union of any two or more substances to form a physically-homogeneous mass, and into a product which cannot be mechanically divided into dissimilar parts. Under this definition nearly every operation of chemistry would be synthetical; for, even in the case where an element is isolated, this is done only at the expense of some other bodies which pass into the condition of compounds; thus, when gold is precipitated in a metallic state from solution, we must use iron, zinc, or some other substance, which shall become oxidized and dissolved in the place of the precipitated gold.
Most cases of synthesis take place with great facility, automatically in fact, for, when coal is burned, we start the fire, and after that the oxygen and carbon unite to form carbonic acid, without any further effort on our part.
Now, in the world there are vast numbers of distinct compounds, some of which have a simple and others a complex structure; it is found, by long experience, that there is a general disposition on the part of these substances to pass from the state of feebly-united units to that of great fixity; thus, wood, which is composed of carbon, oxygen, and hydrogen principally, burns in the air into two stable and incombustible bodies, carbonic acid and water; and, in so doing, evolves a large amount of heat. Neither of these final products, so formed, can in any way be caused to evolve a further amount of energy, without bringing in the aid of external matter; dynamically, they are dead, as physiologically an animal is, when no longer capable of movement.
To raise a body into a state so that it contains within itself force in a potential form, and so as to be able to liberate this force spontaneously, when certain conditions are fulfilled, is an operation opposed to the general tendencies of the material world, and directly contrary to what may be called the habits of non-vitalized matter. Now, it is precisely this thing, this act of elevating some limited portion of matter to a higher plane, where its potentiality and complexity are both increased, that is meant by chemical synthesis, and it will be seen how much this use of the term restricts the meaning of the words as ordinarily used.