In more recent times the great extension of trade to the farthest countries of the globe, and still more the progress of chemistry, have made us familiar with a number of new perfumes. More than two hundred different aromatic substances are now known, and still they are far from being exhausted; every year new odoriferous plants become known, from which the chemist extracts perfumes. By this means, as well as by the enormous employment of perfumes in all grades of society, the art of their preparation has risen to a higher plane; out of empiricism, which alone prevailed a few decades ago, into the domain of the chemical sciences. Since the appearance of the last edition of this book, the art of perfumery has made noteworthy progress both with reference to the knowledge of new aromatic substances and to improvement in the methods of their preparation; by the introduction of glycerin, solid and liquid vaselin, and salicylic acid into perfumery, one of its branches—hygienic cosmetics—has made an important advance. At present it is particularly France and England whose perfumery industry is most extensive and which to some extent rule the markets of the world; southern France and Algiers especially furnish the best raw materials, the finest essential oils for the manufacture of perfumes at the chief centres, Paris and London. CHAPTER II. ABOUT AROMATIC SUBSTANCES IN GENERAL. We apply the term perfume—which really means a fumigating material—to those substances which make an agreeable impression upon our sense of smell; the French call them briefly _odeurs_, _i.e._, odors. The high degree of development at present attained by this industry in France and England is the cause of the fact that all perfumes are generally sold under French or English names, which must be borne in mind by manufacturers in this country. Perfumes or scents, however, exert not only an agreeable impression on the olfactory organ, but their effect extends to the entire nervous system, which they stimulate; when used in excess, they are apt to cause headache in sensitive persons; the laborers in the chemical factories where these substances are produced on a large scale, occasionally even suffer by reason of their stimulating action on the nerves. For this reason perfumes should never be employed otherwise than in a very dilute condition; this necessity arises from a peculiarity of the odorous substances which when concentrated and pure have by no means a pleasant smell and become fragrant only when highly diluted. Oil of roses, of orange flowers, or of jasmine, in fact nearly all aromatic substances, have an almost disagreeable odor when concentrated; only in an extremely dilute state they yield those delightful scents which we admire so much in the blossoms from which they are derived.