There are two other rubber-producing plants, neither of which are as important as Hevea and Castilla. One is the common rubber plant so much grown as a house plant and said to be much cherished for that purpose in Brooklyn. It is a kind of fig tree, known as Ficus elastica, a native of India and the source of India rubber. It was used for years, before the days of vulcanization, mostly for lead-pencil erasers. Thousands of acres of it in India were recently destroyed to make room for Hevea, although it still produces a respectable amount of rubber, inferior, however, to Hevea and Castilla. In Mexico a new source of rubber is the guayule rubber plant, a small shrub native of the drier parts of the Mexican uplands. It does not produce latex, as practically all other rubber plants do, but particles of rubber are found directly in its tissues, mostly in the bark. While of some importance, this shrub, known as Parthenium argentatum, a member of the Compositæ or daisy family, is not likely to become a dangerous rival of either Para or Castilla rubber. Wild sources of guayule rubber are already reported as diminishing rapidly, so that its permanent success will depend upon cultivation. At least a score of other plants are known to produce rubber of a kind, but none of them have yet been much developed. From most plants with a milky juice, such as dogbane or spurge, rubber of some sort can usually be recovered. The production of this substance is directly due to a response of the plant to wounds, and there are still great fields of research necessary on this phase of plant activity, upon which a great industry has already been built.
5. Drugs
Nearly all the drugs and medicines of importance are of vegetable origin, and from the days of Theophrastus the study of plants as possible medicines has been one of the chief phases of botanical research. In the early days all that was known about plants was learned by men interested in medicine, and some of their quaint old books are interesting relics of a bygone day. At present, pharmacognosy, or the science of medicinal plant products, is a highly developed specialty taught in medical and pharmacy schools. And yet the greatest medical college in this country has recently issued instructions to its staff of doctors and nurses to pay particular attention to “old wives’ remedies,” most of which consist of decoctions of leaves and other parts of plants. They have done this because all the knowledge of the scientists regarding medicinal plants has its origin in the habit of simple people turning to their local plants for a cure. The accumulation of the ages, aided and guided by the scientist, has resulted in the wonderful things that can now be done to the human body through the different drugs, nine-tenths of which are of plant origin.
There is almost no part of a plant that, in some species at least, has not been found to contain the various acids, alkaloids, oils, essences, and so forth, which make up the chief medicinal or, as the pharmacists call it, the active principle of plants. In certain of them the most violent poisons are produced, such as the poison hemlock which killed Socrates, and the deadly nightshade. And again the unripe pod of one plant produces a milky juice so dangerous that traffic in it is forbidden in all civilized countries, and yet later the seeds from that matured pod are sold by the thousands of pounds to be harmlessly sprinkled on cakes and buns by the confectioners. Earlier in this book it was said that plants are chemical laboratories, and nowhere has this alchemy been carried to such a pitch of perfection as in the hundreds of drugs produced by different plants. Reference to special books on that subject should be made by those interested, as only a few of our most important drug plants can be mentioned here.
QUININE
The Spanish viceroy of Peru, whose wife, the Countess del Chinchón, was dangerously ill of a fever in that country about 1638, succeeded through the aid of some Jesuit priests in curing the malady, with a medicine which these priests had gotten from the natives. It was a decoction from the bark of a tree, and its fame soon spread throughout the world as Peruvian bark. Even in those days malaria was the curse of the white man in tropical regions, and since then it is hardly too much to say that the discovery of this drug has made possible for white colonists the retention of thousands of square miles of tropical country that without it would in all probability be unfit for occupancy. To the natives, too, quinine has been one of the greatest blessings, and in some of the remote regions of the tropics the writer has found quinine more useful than dollars in getting help from fever-ridden natives, too poor and too remote from civilization to get the drug.
For more than a hundred and fifty years after the discovery of Peruvian bark it was always taken as a liquid, usually mixed with port, and an extremely noxious and bitter drink it made. The fine white powder which we now use in tasteless pellets or pills has made the drug even more useful than before.
The trees from which the bark is used all belong to the genus Cinchona, named for the first distinguished patient to benefit by it, and belong to the Rubiaceæ or madder family. There are at least four or five different species. For many years Peru and near-by states were the only source of the bark, and the English became convinced that the great trade in the drug would exterminate the tree, so in 1880 they introduced the plant into India. These cinchona plantations now provide most of the world’s demand, and some idea of what that means may be gleaned from the fact that in Ceylon alone over fifteen million pounds of the drug are produced annually. In India itself the plantations are largely government owned and quinine is sold in the post offices at a very low rate. In cinchona plantations strips of the bark are removed, and after a proper period of healing, the process is repeated. It takes about eight years before it is safe to begin cutting the bark.
ACONITE
Most doctors use aconite for various purposes and it is mentioned here chiefly as illustrating a common characteristic of many medicinal plants. The whole plant is deadly poisonous, and in the root there appears to be a concentration of this poisonous substance, which makes the plant one of the most dangerous known. All of the drug aconite is derived from Aconitum Napellus, a monkshood, belonging to the buttercup family. It is a perennial herb with beautiful spikes of purple-blue flowers, not unlike a larkspur, and is a native of temperate regions of the Old World. A related Indian species has been used for probably thousands of years by the natives. They poison their arrows with it and so deadly is the drug that a tiger pricked by such an arrow will die within a few minutes. It is conceded to be the most powerful poison in India. Numerous accidents have resulted in Europe from careless collectors of the roots of horseradish, who sometimes get aconite roots mixed with that condiment, usually with fatal results.