whose presence would be injurious to the organism, we must also take into consideration that we may not he able to attain our object by a single process, but by a whole series of altogether different processes—only by a most careful observation of all these points can we arrive at results which will allow us to draw conclusions with reference to the corresponding processes in the body.
It may appear remarkable that, in the syntheses which have been made, these conditions were not considered; but it must not be forgotten that a chemist makes a synthesis for its own sake, unconcerned whether he attains his result in the same manner as the organism. He can only attempt the solution of this question when he knows the steps by which the structure is built up. But in this respect we are still far behind, for our knowledge of the chemical properties of the bodies which we find in the organism is still very incomplete. The substances which are most important in the economy of the organism, the albuminoids, notwithstanding the labor and time employed, are very little known, and the same may be said of other substances, such as the bile, the nerve-substance, etc. We do not even know whether the albuminoids and similar compounds have ever been obtained in a pure state; their composition is, therefore, only approximately known; the question, whether the ash which they leave on burning is an essential constituent or an impurity, still remains undecided, and a good method for separating the different members of larger groups is a pious wish. The changes and decompositions of these substances are only known in general; in many cases we know the final but not the intermediate products, which are of the highest importance, as, without doubt, the organism operates with these. Here, above all, it is necessary to throw some light on the obscurity which surrounds this problem, and the necessity will best be shown by an example. If albuminoids are treated with digestive ferments, or with dilute acids, there is at first produced a series of peculiar compounds still similar to the albuminoids, called peptones. If the latter are exposed to the action of strong acids or alkalies, they are finally decomposed into amido acids; at the same time carbonic acid, ammonia, oxalic acid, and other simple compounds, are formed in small quantities. Although completely justified in assuming that the elements of water have been taken up in these processes, it is not positively known in what relation the peptones stand toward the albuminoids; whether the peptones produced from various albuminoids are different or identical, or whether only one or several peptones are produced from each albuminoid; whether they are crystallizable or not; whether the peptones are directly decomposed into amido acids, or whether further intermediate products are formed—in short, we are only beginning those investigations which promise to give the most important results.
Fortunately, the organism also contains more simple compounds, which are well known, and the formation of which can be discovered