had to be applied.  The mere finding out of percentage composition tells us little or nothing about an organic compound.  What the elements are that compose the compound is not to be found out.  That can be told beforehand with almost absolute certainty.  What is wanted is to know how the atoms of carbon, hydrogen, oxygen, and nitrogen are linked together, for, strange to say, these differences of groupings, which may be found to exist between these three or four elements, endow the compounds with radically different properties and serve us as a basis of classification.

The development of this part of chemistry, therefore, required very different methods of research.  Instead of at once destroying a compound in order to learn of what elements it was composed, we submit it to a course of treatment with reagents, which take it apart very gradually, or modify it in the production of some related substance.  In this way, we are enabled to establish its relations with well defined classes and to put it in its proper place.  Of equal importance with the analytical method of study, however, is the synthetical.  This method of research, as applied to organic compounds, embodies in it the highest triumphs of modern chemistry.  It has been most fruitful of results, both theoretical and practical.  Within recent years, hundreds of the products of vegetable and animal life have been built up from simpler compounds.  Thousands of valuable dye-colors and other compounds used in the arts attest its practical value.  It may, therefore, seem anomalous when I say that one of the most important of all the classes of organic compounds has not shared in this advance.  The alkaloids, that most important class from a medical and pharmaceutical point of view, have until quite recently been defined in the books simply as “vegetable bases, containing nitrogen.”  Whether they were marsh-gas or benzol derivatives was not made out; how the four elements, carbon, hydrogen, oxygen, and nitrogen, were grouped together in them was absolutely a thing unknown.  Chemists all admitted two things—­first, that their constitution was very complex, and, second, that the synthesis of any of the more important medicinal alkaloids would be an eminently desirable thing to effect from every point of view.  Within the last five years, however, quite considerable progress has been made in arriving at a clearer understanding of these most important compounds, and I shall offer to your attention this evening a brief statement of what has been done and what seems likely to be accomplished in the near future.

It was early recognized that the alkaloids were complex amines or ammonia derivatives.  The more or less strongly marked basic character of these bodies, the presence of nitrogen as an essential element, and, above all, the analogy shown to ammonia in the way these bases united with acids to form salts, not by replacement of the hydrogen of the acid, but by direct addition of acid and base, pointed unmistakably to