tion has been made out." Within a few years chemists have announced the synthesis of many acids, essential oils, alkaloids, glucosides, dye-stuffs, and other bodies naturally occurring in the organic world, and so rapidly do these announcements succeed one another that expectation has displaced surprise. Noteworthy are the following: Alizarine, the valuable coloring-matter of madder; vanilline, the aromatic principle of the vanilla bean; cu marine, the aromatic principle of the Tonka bean; indigo, the well-known dye-stuff; uric acid, an animal product; tyrosin, likewise a product of the animal organism; salicine, daphnetine, and umbelliferone, natural glucosides and related bodies; piperidine, a constituent of pepper; and cocaine, the new anæsthetic. Besides these, many syntheses have been accomplished of bodies isomeric and not identical with the natural products.
The alchemists labored to transmute base metals into noble ones, and were destined never to realize their ambitious designs; modern organic chemists, operating on substances compared with which even the base metals are precious, produce articles more beneficial to mankind than gold itself, and, at the same time, gain, indirectly, no small store of the coveted metal.
The application of chemistry to physiology encounters the most complex and difficult problems in the science, and at the same time aims to accomplish the most beneficent results. "The physiologist complains that probably ninety-five per cent of the solid matters of living structures are pure unknowns, and that the fundamental chemical changes which now occur during life are entirely shrouded in mystery. It is in order that this may no longer be the case that the study of carbon compounds is being so vigorously prosecuted." It may seem strange to the non-professional in this audience that, in spite of persistent and skillful attempts to solve the problem, chemists are obliged to admit ignorance of the exact composition of so common a substance as the white of egg; yet, until they acquire an accurate knowledge of the constitution of albuminous substances, the processes of animal economy can not be explained. While the physiologist, in some degree, waits on the organic chemist for further developments, the latter discovers and prepares novel bodies much faster than the physiologist ascertains their influence on the animal economy. To the joint labors of chemists and physiologists are due the blessings of anæsthetics, hypnotics, and other conquerors of suffering and disease. The anæsthetic properties of cocaine, and the circumstances of their discovery, are matters of popular knowledge. Within a twelvemonth, ethyl-urethane has been added to the list of hypnotics.
In recent years sanitary chemistry has acquired great importance, and now occupies a distinctly defined field, including all that pertains to the hygienic value of foods and beverages, their adulterations, and their fraudulent substitutes; questions of gas and water supply; of the uses and abuses of disinfectants; of household ventilation, and of
