Definition

Materia Medica or Pharmacognosy, for the terms as used by pharmacists are synonymous, may be defined as that science which aims at a complete and systematic knowledge of crude drugs of animal or vegetable origin. The term drugs may be understood to include all parts of animals or vegetables used in medicine, or such of their products as have not undergone any material elaboration or separation into their constituents; it is, however, not susceptible of exact limitation, and hence substances may be included which are of dietetic or technical rather than medicinal use.

A complete knowledge of a drug must include a knowledge of the morphological nature and the structure, both macroscopic and microscopic, of such as are organised, of the botanical or zoological source, of the constituents both active and inactive, their nature, the amounts in which they are present, and the relation they bear to the constituents of other drugs. The geographical source, the cultivation, mode of collection, preparation for the market, the trade route, commercial varieties, history, uses, etc, must also be known. To attain this knowledge the aid of chemistry and of chemical methods of investigation, of botany and botanical methods, of physiology, geography, commerce, history, etc, must be sought, or at least the results of other investigators in these respects utilised, and the information thus obtained combined to form a complete knowledge of each drug, and these systematised to build up the science of pharmacognosy.

Pharmacognosy may be subdivided into Scientific Pharmacognosy, as above described, and Applied Pharmacognosy. Applied Pharmacognosy is the application of scientific pharmacognosy to the solution of the pharmacognostical problems that are constantly arising in the daily work of the pharmacist. Thus Scientific Pharmacognosy includes an intimate knowledge of the structure of vegetable drugs; Applied Pharmacognosy utilises this knowledge to identify the drug entire or in powder and to determine its purity. Scientific Pharmacognosy treats of the constituents of drugs. Applied pharmacognosy ascertains the relative quality of a drug by determining the proportion in which one or more of these constituents is present.

History

Although it is only within very recent years that pharmacognosy has substantiated its claim to rank as a science, the collection of herbs for medicinal use is of the remotest antiquity. Ancient Egyptian papyri, of which that of Ebers written about 1600 B.C. is the most important and most complete, prove that even at this early period the physicians were in possession of a very considerable number of drugs, including aloes, acacia gum, myrrh, Indian hemp, hemlock, opium, frankincense, cassia, cummin, coriander, castor seed, and many others. But as far as Western nations are concerned, Greece may be regarded as the cradle of medicine. About the middle of the twelfth century before the Christian era temples were built which served as centres for the exercise of the healing art. Most famous among these were the temples of the deified ∆sculapius at Epidaurus, Cos, Trika, and Pergamos. At these temples, which were usually situated on high ground in pure air, cures were effected chiefly by hygienic means such as massage, baths, etc. Pythagoras (580 B.C.) added to this hygienic treatment the use of such drugs as squill and mustard. Hippocrates (b.c. 466), who placed the treatment of disease on a more rational basis, was familiar with numerous indigenous as well as exotic drugs, with many of which he doubtless became acquainted during his travels. Wormwood, acacia gum, chamomile, cinnamon, hemlock, gentian, henbane, myrrh, rhubarb, and many others were well known to him.

Theophrastus (about 370 B.C.) was a pupil of Aristotle, after whose death he became chief of the Aristotelian school. He enumerates some 500 plants which were known to him, distinguished cinnamon from cassia, and was acquainted with ergot. It was during this period (335-325 B.C.) that Alexander the Great undertook his expeditions to Persia, India, and Africa, as the result of which numerous treasures, and among them drugs, were brought back to Greece.

Alexander founded Alexandria, which he intended to become the seat of the learning and commerce of the world. Although science in Egypt had fallen so low that the Greeks learnt but little from the Egyptians, the Alexandrian school was invaluable in preserving and transmitting to posterity the writings of Greek and other authors.

After the death of Alexander the Roman Empire rose. During this period Dioscorides, who was a Greek by birth, travelled in Egypt, Africa, Spain, Italy, and Syria, where he became acquainted with a great variety of plants and drugs. His observations and knowledge he placed on record in a compendious work on pharmacognosy which served for many centuries as an inexhaustible source of information. This remarkable work contains classified descriptions of a great number of vegetable, animal, and mineral drugs, no fewer than 500 medicinal plants, including many exotic ones, being discussed. To Dioscorides belongs the credit of being the first to separate pharmacognosy from medicine.

Pliny, who lived about the same time as Dioscorides and evidently made use to some extent of the same sources of information, studied natural history; his work on this subject consisted of forty-seven books, many of which have been unfortunately lost, Pliny himself perishing in the eruption of Vesuvius (a.d. 79). His ' Natural History,' in addition to books dealing with zoology, meteorology, astrology, etc, treats of as many as 1,000 plants.

Galen (a.d. 131 to 200) was a physician and studied chiefly the production of various ' galenical' preparations, dealing only incidentally with drugs. He recognised the adulteration of cinnamon, pepper, saffron, and myrrh, and points out that exhausted rhubarb was sold in place of the genuine. He wrote twenty books containing a large number of receipts for various preparations.