such appeal having as its basis the fact that among insects themselves olfactory sensibility has in many cases been developed in their own mating.[54] There is, for example, a moth in which both sexes are similarly and inconspicuously marked, but the males diffuse an agreeable odor, said to be like pineapple, which attracts the females.[55] If, therefore, the odors of flowers have developed because they proved useful to the plant by attracting insects or other living creatures, it is obvious that the advantage would lie with those plants which could put forth an animal sexual odor of agreeable character, since such an odor would prove fascinating to animal creatures.  We here have a very simple explanation of the fundamental identity of odors in the animal and vegetable worlds.  It thus comes about that from a psychological point of view we are not really entering a new field when we begin to discuss the influence of perfumes other than those of the animal body.  We are merely concerned with somewhat more complex or somewhat more refined sexual odors; they are not specifically different from the human odors and they mingle with them harmoniously.  Popular language bears witness to the truth of this statement, and the normal and abnormal human odors, as we have already seen, are constantly compared to artificial, animal, and plant odors, to chloroform, to musk, to violet, to mention only those similitudes which seem to occur most frequently.

The methods now employed for obtaining the perfumes universally used in civilized lands are three:  (1) the extraction of odoriferous compounds from the neutral products in which they occur; (2) the artificial preparation of naturally occurring odoriferous compounds by synthetic processes; (3) the manufacture of materials which yield odors resembling those of pleasant smelling natural objects. (See, e.g., “Natural and Artificial Perfumes,” Nature, December 27, 1900.) The essential principles of most of our perfumes belong to the complex class of organic compounds known as terpenes.  During recent years a number of the essential elements of natural perfumes have been studied, in many cases the methods of preparing them artificially discovered, and they are largely replacing the use of natural perfumes not only for soaps, etc., but for scent essences, though it appears to be very difficult to imitate exactly the delicate fragrance achieved by Nature.  Artificial musk was discovered accidentally by Bauer when studying the butyltoluenes contained in a resin extractive.  Vanillin, the odoriferous principle of the vanilla bean, is an aldehyde which was first artificially prepared by Tiemann and Haarmann in 1874 by oxidizing coniferin, a glucoside contained in the sap of various coniferae, but it now appears to be usually manufactured from eugenol, a phenol contained in oil of cloves.  Piperonal, an aldehyde closely allied to vanillin, is used in perfumery under the name of heliotropin