This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
Fig. 6. - Vase of otto of rose.
Fig. 7. - Leaden canisters of star-anise oil.
Fig. 8. - Sampling a few bales of bark. (Heap).
Fig. 9. - Sale room of Messrs. Hale & Son. On the centre and window-tables various drugs; on the table to the left chiefly bristles; on the floor sample-bags of drugs. (Heap).
Fig. 10. - A drug and gum show at London Docks. (Heap).
Fig. 11. - Show of drugs at London docks; a, cinnamon bark; b, cinchona bark; c, Zanzibar cloves; d, various bales of drugs. (Heap).
Fig. 12. - Bales of drugs in London Docks. (Heap).
Sometimes drugs are 'worked' before they are sold; they are then usually emptied on to the floor of the warehouse, mixed or sorted as required, and repacked in the cases. Spices such as pepper, cloves, ginger, nutmeg, cassia, pimento, and chillies, together with tapioca and arrowroot, are included in the spice sales. Cinnamon auctions are held once a month.
After arrival in the drug merchants' warehouse the drugs have to undergo further treatment before they are sold to the pharmacist.
Fig. 13. - Working tragacanth. (Heap).
They are examined, freed from dust and dirt by sifting, and graded either by sifting or hand-picking; they have frequently to be further tested by assay. Few drugs, therefore, reach the pharmacist in the condition in which they are imported.
The various parts of plants intended for medicinal use contain, when freshly collected, a large proportion of water from which they must be freed unless they are destined to be used in the fresh state. The following table,1 which gives the approximate amounts of air-dry drug yielded by 100 parts of the fresh plant, will suffice to indicate the limits within which the percentage of moisture usually varies: -
1 Tschirch, Handbuch d. Pharmakognosie.
Red Poppy Petals
Arnica Flowers .
Sweet Flag Rhizome
Couch Grass .
During the process of drying certain changes occur which are produced, in part at least, by the action of enzymes contained in the cells. These changes may affect the colour of the drug and so become evident to the eye; thus the scarlet of the red poppy petal becomes dull violet, the green of leaves may turn to black, and gentian root, which is normally white, may acquire a reddish brown colour. They may also affect the odour of the drug; thus vanilla pods, valerian roots, orris rhizomes and other drugs acquire their characteristic odour during the process of drying. They may also affect certain constituents of the drug without producing any readily perceptible change; thus the gentiopicrin present in fresh gentian root may be completely decomposed. When the drug is quite free from moisture (not simply air-dry) these changes cease and so long as the drug is kept quite dry they cannot be resumed. The procedure adopted in drying drugs depends therefore upon whether the action of the enzymes is necessary and should be encouraged or whether it is prejudicial and should be avoided. In the former case slow drying and the maintenance of a temperature at which the enzymes are most active are indicated (compare vanilla, tea, cocoa, &c). In the latter case the drying should be conducted as rapidly as possible in order to render the enzymes inactive before they have appreciably affected the constituents of the drug. Rapid drying is accomplished by exposing the drugs in thin layers to a free current of air at a temperature of about 35° to 40°. They may be scattered upon wire-netting trays (leaves not overlapping one another and roots sliced longitudinally or transversely) and placed in a well-ventilated loft; or vertical columns of such trays, 6 or 8 inches apart, may be formed in the open air and covered with roofing; or the trays may be assembled in a long narrow shed through which warm, dry air is driven. Open-air drying is often resorted to in hot climates.
Drugs that have been completely dried usually re-absorb about 10 per cent, of moisture when exposed to the atmosphere; they are then termed ' air-dry.' Even in air-dry drugs changes may occur; such changes are often prejudicial as they are for instance in Indian hemp and foxglove leaves. In the case of Indian hemp the change is probably simple oxidation of the cannabinol contained in it, but in the case of foxglove leaves and many other drugs enzyme action is certainly involved.
Two methods of obviating such enzyme action may be adopted. By the first the drugs are completely dried and maintained in that state in hermetically sealed containers or in well-closed vessels over quicklime. Flowers, kept absolutely dry over quicklime, will retain their natural colours for years and foxglove leaves their constituents unimpaired.
The second method consists in rendering the enzymes inactive before the drugs are dried. This may be effected by exposing them for a short time to the vapour of alcohol under moderate pressure at a temperature of about 95°. Life in the plants is arrested and all the enzymes killed without raising the temperature of the plants above about 80°. Fresh kola nuts may be sterilised by exposing them to steam under pressure at a temperature of about 110°. By such means the drugs are rendered stable and the process is termed ' stabilisation.'
Air-dry drugs kept in parcels, sacks, barrels, etc, are liable to be attacked by certain insect pests. Sayre 1 enumerates about 25.
The commonest of these insect pests belong either to the Coleoptera (beetles) or Tyroglyphidae (mites).
Among the Coleoptera the most frequent and most destructive is the drug room bettle (Sitodrepa panicea). This beetle lays its eggs in the summer in crevices in the cork of roots, etc. The young larva drills a tunnel into the drug, hibernates through the winter, passes into the pupa stage in the early summer and finally emerges as a perfect insect about June or July. Dandelion root, burdock root, aconite root, belladonna root, ginger, nutmegs are particularly liable to attack.
The cigarette beetle (Lasioderma serricorne), the granary beetle (Niptus hololeucus), and Ptinus brunneus also do great damage.
Among the Tyroglyphidae various species of Tyroglyphus appear to be the commonest. In this case the larva resembles the perfect insect but is smaller and has only six legs instead of eight. It possesses two pairs of strong mandibles with which it tears the drug into small pieces before ingestion. The mites are very minute but they often occur in prodigious numbers. Quince seed, ergot, cantharides, ground linseed and many powdered drugs are liable to be attacked.
Drugs may be protected from insect pests by keeping them quite dry, or by dusting them with lime which blocks up the breathing apparatus of the mature insect and of the larva. Drugs already infested may be freed from them by exposing them to the vapour of carbon tetrachloride, carbon disulphide, chloroform, etc, by which larvae and mature insects are destroyed.
Vegetable drugs kept in too damp a place are liable to develop moulds, bacteria, yeasts, etc. These organisms are compelled to obtain part at least of their nourishment from organic substances and in doing so frequently produce ammonia, sulphuretted compounds, etc. The attacks of these organisms may also be warded off by keeping the drugs quite dry.
1 American Journ. Pharmacy, 1893, p. 321.