THE AROMATIC VANILLA. 193 they are afterwards rubbed over with oil, and in this state sent to market. Fig. 81. Vanilla aromatica-The Aromatic Vanilla. Scalo for flowers and fruit, 1 inch to 6 inches. The odoriferous principles of the vanilla have not yet been accurately determined. One of them is a peculiar fragrant volatile oil, and another a fragrant acid, probably the cinnamic. Hence the similarity of the odour of vanilla to that of the balsams. As a perfume, vanilla is highly esteemed. Its principal use, however, is in flavouring chocolate, ices, creams, and other confectionery. Coffee, and even tea, are sometimes also flavoured with it. Physiologically, it acts upon the system as an aromatic stimulant, exhilarating the mental functions, and increasing generally the energy of the animal Vor. II-9 Fig. 82. a Dipterix odorata-The Tonka Bean tree. Leaves and raceme of flowers, 1 inch to a. flower; b. kernel or bean; c. pod or fruit. 1 inch to 2 inches. system. Like some other odours—those of camphor and patchouli, for example -that of vanilla sometimes exhibits narcotic ef fects upon those who are much exposed to it. Five or six hundred weight of vanilla are yearly imported into this country. e. Coumarin.-Nearly allied to the fragrant resins is an interesting and widely diffused natural perfume, to which chemists have given the name of coumarin. A fragrant bean, the Tonka or Tonga bean (fig. 82), the fruit of the Dipterix odorata, formerly well known in this country, and much employed for perfuming snuff, contains this substance coumarin. Alcohol readily extracts it from the bean; and by evaporating the alcoholic solution, we obtain the substance in a solid state. It forms white brilliant needles, possessed of an agreeable aromatic odour. When heated, it rises in vapour; and this vapour, when inhaled, acts powerfully upon the brain. It consists of carbon, hydrogen, and oxygen in the following proportions: THE TONKA BEAN, So that it is richer in oxygen than any of the volatile oils of which the composition has been given above. But the interesting circumstance in the history of this substance is, that, though discovered first in a foreign bean, the produce of a warm climate, it has since been found to exist in, and to impart their well-known agreeable odours to, several of our most common European plants. Among these, the sweet-scented vernal grass (fig. 83), to which we are in the habit of ascribing the fragrance of well-made hay, deserves especial Fig. 83. 195 mention. This grass contains cou- Anthoxanthum odoratum- marin, and imparts to dry hay the odour of this substance. Sweet-scented vernal grass. sweet-smelling plants in The following is a list of the which coumarin has already been found :— Dipterix odorata, or Tonka bean. Angræcum fragrans, the Faham tea-plant of Mauritius. Anthoxanthum odoratum, the sweet-scented vernal grass. Melilotus cærulea, the blue or Swiss melilot. It is the same odour, therefore, which gives fragrance to the Tonka bean, to the Faham tea of the Mauritius, to our melilot trefoil, and to sweet-smelling hay-fields, in which melilot and vernal grass abound. In Switzerland the blue melilot is mixed with particular kinds of scented cheese, and the coumarin it contains gives to that of Schabzieger its peculiar well-known odour. Many other sweet-smelling grasses are known, such as Hierochloe borealis, Ataxia horsfieldii, Andropogon Iwacancusa, Andropogon schoenanthus or lemon grass, &c. &c., in which coumarin probably does not exist. Indeed, the Andropogon muricatus (the kuskus of India) yields a favourite fragrant oil, used as a medicine in that country. There are other sweet-smelling substances therefore, without doubt, from which grasses dried for hay, in different countries, may derive an agreeable odour. I have alluded to the influence which, in the form of vapour, coumarin exercises upon the brain. It is not improbable that the hay fever, to which many susceptible people are liable, may be owing to the presence of this substance in the air in unusual quantity* during the period of hay-making. In seasons which are peculiarly hot, and in localities where the odoriferous grasses occur in uncommon plenty, such an abundance of coumarin vapour in the air is by no means unlikely to occur. *Such fevers may possibly arise also from the diffusion through the air of the pol len of these odoriferous plants. This pollen is supposed, like that of the kalmias and rhododendrons, to possess narcotic properties, and, when drawn in by the nose and mouth, to produce narcotic fever-causing effects upon the system. CHAPTER XXV. THE ODOURS WE ENJOY. THE VOLATILE ETHERS AND ANIMAL ODOURS. Wine ether, how prepared.-Nitric ether and acetic ether.-Wood spirit and wood ether.-Potato spirit, or oil of grain, and potato ethers.-Oil of winter-green, a natural ether; how prepared artificially.-Sweet-smelling ethers manufactured as perfumes.-Pear oil, or essence of jargonelle.-Apple oil.-Grape and cognac oils. -Pine-applo oil-Essence of melons.-Essence of quinces.-Hungarian wine oil, and other artificial fragrances.-Caprylic ethers.-The flavour of whisky.-Propylic ethers. The bouquet of wines.-Œnanthic ether gives the generic flavour to grape wines.-Characteristic fragrant principles of different wines.-Use of the sweet flag in flavouring spirits and beer; its abundance in Norfolk.-Odoriferous substances of animal origin.-Musk; the musk deer; lasting smell of musk.Civet.-Effect of dilution upon odoriferous substances.-Use of civet in Africa.Castoreum and hyraceum.-Ambergris and perfumes prepared from it.-Insect odours.-General reflections.-Extreme diffusiveness of odours.-Delicacy of the organs of smell.-How chemistry increases our comforts, gives rise to new arts, and generally civilizes. II. THE VOLATILE ETHERS yielded by plants are at the present moment the most interesting to the chemist of all the natural perfumes. This interest arises from the cir cumstance that a careful analytical examination of some of those produced in living plants, has given us the key not only to the true chemical composition of these substances themselves, but also to the mode of producing by art an almost endless variety of odoriferous compounds. |